Abstract: Medial prefrontal cortical areas have been hypothesized to underlie altered contextual processing in posttraumatic stress disorder (PTSD). We investigated brain signaling of contextual information in this disorder. Eighteen PTSD subjects and 16 healthy trauma-exposed subjects underwent a two-day fear conditioning and extinction paradigm. On day 1, within visual context A, a conditioned stimulus (CS) was followed 60% of the time by an electric shock (conditioning). The conditioned response was then extinguished (extinction learning) in context B. On day 2, recall of the extinction memory was tested in context B. Skin conductance response (SCR) and functional magnetic resonance imaging (fMRI) data were collected during context presentations. There were no SCR group differences in any context presentation. Concerning fMRI data, during late conditioning, when context A signaled danger, PTSD subjects showed dorsal anterior cingulate cortical (dACC) hyperactivation. During early extinction, when context B had not yet fully acquired signal value for safety, PTSD subjects still showed dACC hyperactivation. During late extinction, when context B had come to signal safety, they showed ventromedial prefrontal cortex (vmPFC) hypoactivation. During early extinction recall, when context B signaled safety, they showed both vmPFC hypoactivation and dACC hyperactivation. These findings suggest that PTSD subjects show alterations in the processing of contextual information related to danger and safety. This impairment is manifest even prior to a physiologically-measured, cue-elicited fear response, and characterized by hypoactivation in vmPFC and hyperactivation in dACC.

Abstract: The central amygdala (Ce), particularly its medial sector (CeM), is the main output station of the amygdala for conditioned fear responses. However, there is uncertainty regarding the nature of CeM control over conditioned fear. The present study aimed to clarify this question using unit recordings in rats. Fear conditioning caused most CeM neurons to increase their conditioned stimulus (CS) responsiveness. The next day, CeM cells responded similarly during the recall test, but these responses disappeared as extinction of conditioned fear progressed. In contrast, the CS elicited no significant average change in central lateral (CeL) firing rates during fear conditioning and a small but significant reduction during the recall test. Yet, cell-by-cell analyses disclosed large but heterogeneous CS-evoked responses in CeL. By the end of fear conditioning, roughly equal proportions of CeL cells exhibited excitatory (CeL+) or inhibitory (CeL−) CS-evoked responses (∼10%). The next day, the proportion of CeL− cells tripled with no change in the incidence of CeL+ cells, suggesting that conditioning leads to overnight synaptic plasticity in an inhibitory input to CeL− cells. As in CeM, extinction training caused the disappearance of CS-evoked activity in CeL. Overall, these findings suggest that conditioned freezing depends on increased CeM responses to the CS. The large increase in the incidence of CeL− but not CeL+ cells from conditioning to recall leads us to propose a model of fear conditioning involving the potentiation of an extrinsic inhibitory input (from the amygdala or elsewhere) to CeL, ultimately leading to disinhibition of CeM neurons.

Abstract: Current fear-avoidance models consider fear of pain as a key factor in the development of chronic musculoskeletal pain. Generally, the idea is that by virtue of the formation of associations or acquired propositional knowledge about the relation between neutral movements and pain, these movements may signal pain, and hence start to elicit defensive fear responses (eg, avoidance behavior). This assumption has never been investigated experimentally. Therefore, we developed a pain-relevant fear conditioning paradigm using a movement as a conditioned stimulus (CS) and a painful electrocutaneous stimulus as an unconditioned stimulus (US) to examine the acquisition of fear of movement-related pain in healthy subjects. In a within-subjects design, participants manipulated a joystick to the left/right in the experimental (predictable) condition, and upward/downward in the control (unpredictable) condition or vice versa. In the predictable condition, one movement direction (CS+), and not the other (CS-), was followed by painful stimuli. In the unpredictable condition, painful stimuli were always delivered during the intertrial interval. Both fear of movement-related pain ratings and eyeblink startle measures were more elevated in response to the CS+ than to the CS-, whereas no differences occurred between both unreinforced CSs in the control condition. Participants were slower initiating a CS+ movement than a CS- movement, while response latencies to CSs in the control condition did not differ. These data support the acquisition of fear of movement-related pain by associative learning. Results are discussed in the broader context of the acquisition of pain-related fear in patients with musculoskeletal pain.

Abstract: Pavlovian eyeblink conditioning has been used extensively as a model system for examining the neural mechanisms underlying associative learning. Delay eyeblink conditioning depends on the intermediate cerebellum ipsilateral to the conditioned eye. Evidence favors a two-site plasticity model within the cerebellum with long-term depression of parallel fiber synapses on Purkinje cells and long-term potentiation of mossy fiber synapses on neurons in the anterior interpositus nucleus. Conditioned stimulus and unconditioned stimulus inputs arise from the pontine nuclei and inferior olive, respectively, converging in the cerebellar cortex and deep nuclei. Projections from subcortical sensory nuclei to the pontine nuclei that are necessary for eyeblink conditioning are beginning to be identified, and recent studies indicate that there are dynamic interactions between sensory thalamic nuclei and the cerebellum during eyeblink conditioning. Cerebellar output is projected to the magnocellular red nucleus and then to the motor nuclei that generate the blink response(s). Tremendous progress has been made toward determining the neural mechanisms of delay eyeblink conditioning but there are still significant gaps in our understanding of the necessary neural circuitry and plasticity mechanisms underlying cerebellar learning.

Abstract: Understanding how neuronal network activity contributes to memory formation is challenged by the complexity of most brain circuits and the restricted ability to monitor the activity of neuronal populations in vivo. The developing zebrafish (Danio rerio) is an animal model that circumvents these problems, because zebrafish larvae possess a rich behavioral repertoire and an accessible brain. Here, we developed a classical conditioning paradigm in which 6- to 8-d-old larvae develop an enhanced motor response to a visual stimulus (conditioned stimulus, CS) when it is paired with touch (unconditioned stimulus, US). Using in vivo calcium imaging we demonstrate that CS and US activate different subsets of neurons in the cerebellum; their activity, modulated by learning two-photon laser ablation, revealed that the cerebellum is involved in acquisition and extinction, but not the retention, of this memory.

Abstract: Knowledge of age sensitivity, the capacity of a behavioral test to reliably detect age-related changes, has utility in the design of experiments to elucidate processes of normal aging. We review the application of these tests in studies of normal aging and compare and contrast the age sensitivity of the Barnes maze, eyeblink classical conditioning, fear conditioning, Morris water maze, and rotorod. These tests have all been implemented to assess normal age-related changes in learning and memory in rodents, which generalize in many cases to age-related changes in learning and memory in all mammals, including humans. Behavioral assessments are a valuable means to measure functional outcomes of neuroscientific studies of aging. Highlighted in this review are the attributes and limitations of these measures in mice in the context of age sensitivity and processes of brain aging. Attributes of these tests include reliability and validity as assessments of learning and memory, well-defined neural substrates, and sensitivity to neural and pharmacological manipulations and disruptions. These tests engage the hippocampus and/or the cerebellum, two structures centrally involved in learning and memory that undergo functional and anatomical changes in normal aging. A test that is less well represented in studies of normal aging, the context pre-exposure facilitation effect (CPFE) in fear conditioning, is described as a method to increase sensitivity of contextual fear conditioning to changes in the hippocampus. Recommendations for increasing the age sensitivity of all measures of normal aging in mice are included, as well as a discussion of the potential of the under-studied CPFE to advance understanding of subtle hippocampus-mediated phenomena.

Abstract: We investigated the effect of associative learning on early sensory processing, by combining classical conditioning with in vivo calcium-imaging of secondary olfactory neurons, the projection neurons (PNs) in the honey bee antennal lobe (AL). We trained bees in a differential conditioning paradigm in which one odour (A+) was paired with a reward, while another odour (B-) was presented without a reward. Two to five hours after differential conditioning, the two odour-response patterns became more different in bees that learned to discriminate between A and B, but not in bees that did not discriminate. This learning-related change in neural odour representations can be traced back to glomerulus-specific neural plasticity, which depended on the response profile of the glomerulus before training. (i) Glomeruli responding to A but not to B generally increased in response strength. (ii) Glomeruli responding to B but not to A did not change in response strength. (iii) Glomeruli responding to A and B decreased in response strength. (iv) Glomeruli not responding to A or B increased in response strength. The data are consistent with a neural network model of the AL, which we based on two plastic synapse types and two well-known learning rules: associative, reinforcer-dependent Hebbian plasticity at synapses between olfactory receptor neurons (ORNs) and PNs; and reinforcer-independent Hebbian plasticity at synapses between local interneurons and ORNs. The observed changes strengthen the idea that odour learning optimizes odour representations, and facilitates the detection and discrimination of learned odours.

Abstract: Descriptive studies spanning three decades have identified a broad range of cognitive and behavioral deficits in children with fetal alcohol spectrum disorder (FASD) FASD ranges from fetal alcohol syndrome (FAS), which is the most severe impairment characterized by a distinctive craniofacial dysmorphology, small head circumference, and pre- and/or postnatal growth retardation, to alcohol-related neurodevelopmental disorder (ARND), in which children exhibit significant cognitive and behavioral impairment but lack the distinctive facial anomalies (Hoyme et al, 2005) The long-term adverse effects associated with fetal alcohol exposure are increasingly well known, but many women continue to drink heavily during pregnancy in the US (CDC, 2002) and throughout the world (eg, Croxford & Viljoen, 1999; Riley et al, 2003; Jacobson et al, 2006) As many as 13% of infants born in the US are exposed to varying levels of alcohol during pregnancy, with a higher percentage found among disadvantaged populations (CDC, 2002) Identification of alcohol affected children continues to be difficult due to the lack of specificity in behavioral diagnostic criteria and limited understanding of the pathophysiology of the disorder We have recently identified impaired eyeblink conditioning (EBC) to be a remarkably consistent deficit associated with fetal alcohol exposure (Jacobson et al, 2008) In the 5-year follow-up assessment of a cohort of heavily alcohol-exposed children recruited prenatally, not a single child with full FAS met criterion for conditioning, as contrasted with 750% of controls A large proportion (638%) of the heavily alcohol-exposed nondysmorphic children also failed to meet criterion for conditioning at this age These findings corroborate a report of poorer EBC in a US sample of school-aged, alcohol-exposed children with dyslexia (Coffin et al, 2005) Our study was conducted in Cape Town, South Africa, where there is a very high prevalence of heavy alcohol use during pregnancy in the Cape Coloured (mixed ancestry) community (Croxford & Viljoen, 1999; Jacobson et al, 2008) The estimated incidence of FAS in this population is 18 to 141 times greater than in the US and among the highest in the world (May et al, 2000) This population, composed mainly of descendants of white European settlers, Malaysian slaves, Khoi-San aboriginals, and black African ancestors, has historically comprised the large majority of workers in the wine-producing and fruit-growing region of the Western Cape The high prevalence of FAS is a consequence of the very heavy maternal drinking during pregnancy commonly found in this community, due to poor psychosocial circumstances and the traditional dop system, in which farm laborers were paid, in part, with wine Although the dop system has been outlawed, heavy alcohol consumption persists in certain sectors in urban and rural Cape Coloured communities (Carter et al, 2005; Jacobson et al, 2006), and weekend binge drinking is a major source of recreation for many in the community The EBC deficits we reported in alcohol-exposed children are consistent with animal studies showing that heavy exposure to alcohol during the equivalent of the third trimester of pregnancy in humans disrupts EBC in weanling and adult rats, a deficit that is mediated by a dose-dependent cell loss and altered neural activity in the deep cerebellar nuclei (Green et al, 2002a,b) Binge exposure during this period in rodents is also associated with loss of Purkinje and granule cells in the cerebellum (Dunty et al, 2001; Hamre & West, 1993), even after only 2 days of exposure (Thomas et al, 1998) Heavy alcohol exposure in rats and mice on even a single occasion during synaptogenesis has been found to trigger acute neurodegeneration via enhanced apoptosis of Purkinje cells and other neurons in key components of the neural circuit that mediates EBC, including the deep cerebellar nuclei, cerebellar cortex, pontine nuclei, and inferior olive (Dikranian et al, 2005; Green, 2004) The earliest autopsy studies in humans reporting damaging effects of heavy prenatal alcohol exposure identified errors in cell migration, agenesis or thinning of the corpus callosum, and anomalies in the cerebellum and brain stem (Jones & Smith, 1973; Clarren, 1977; Clarren & Smith, 1978) In the only study to perform a comprehensive morphometric analysis of the four major cortical lobes, cerebellum, and principal subcortical regions, Archibald et al (2001) found a significant deficit in total brain volume, with proportionately greater reductions particularly in the cerebellum, parietal lobe, and caudate nucleus, including a 15% reduction in cerebellar volume in individuals with FAS By contrast, hippocampal volume was not affected Pavlovian conditioning is a culturally neutral, non-verbal form of associative learning, in which the onset of a conditioned stimulus (CS), usually a pure tone, precedes an unconditioned stimulus (US), usually a mild air puff to the eye, which elicits a reflexive eyeblink unconditioned response (UR) With repeated pairings of the tone and air puff, the tone CS comes to elicit an eyeblink response on a large percentage of trials This eyeblink conditioned response (CR) represents the learned association between tone and air puff The operational simplicity and minimal sensory, motor, and motivational demands of the procedure make it applicable with little or no modification across a range of animal species—rodents, rabbits, monkeys, sheep, humans—and across the life-span, beginning in early infancy (Stanton, Claflin & Herbert, 2010) In delay conditioning, the tone CS precedes, overlaps, and co-terminates with the onset of the air puff, whereas in trace conditioning, there is a brief stimulus-free “trace interval” between the offset of the tone and the onset of the air puff (Fig 1) Figure 1 Schematic diagram of trial epochs used in short delay and trace conditioning The neural circuitry involved in eyeblink conditioning has been documented in considerable detail (Woodruff-Pak & Steinmetz, 2000a, b; Woodruff-Pak & Disterhoft, 2008) A brain stem-cerebellar circuit has been identified that is both necessary and sufficient for delay conditioning (McCormick & Thompson, 1984; Thompson, 1986; Lavond et al, 1993; Logan & Grafton, 1995; Kim & Thompson, 1997; Thompson, 2005) In delay conditioning, neural activity representing the tone CS is projected via the colliculus to discrete portions of the pontine nuclei, which convey this information to the cerebellum via mossy fibers in the middle cerebellar peduncle Neural activity representing the air-puff US is projected via the inferior olive to the cerebellum via climbing fiber projections in the inferior peduncle Both pontine and olivary inputs reach Purkinje cells in cerebellar cortex and send collateral inputs directly to the cerebellar deep nuclei (Christian & Thompson, 2003; Lavond & Steinmetz 1989) Neural plasticity in cerebellar cortex and deep nuclei produced by appropriately timed activation of climbing- and mossy-fiber inputs underlies short-delay conditioning (Thompson, 1986, 2005; Krupa et al, 1993; Kim & Thompson, 1997; Ohyama et al, 2003) The essential efferent CR pathway consists of fibers that project from the deep nuclei via the superior cerebellar peduncle to the red nucleus The CR-related neural activity is then projected to the motor neurons that generate conditioned eyeblinks Although this brain stem-cerebellar circuitry is sufficient for delay conditioning, trace conditioning with a 500-ms stimulus-free interval has been shown to engage both the cerebellum and the hippocampus in experiments with laboratory animals (Moyer et al 1990; Stanton et al, 2010; Steinmetz, 2000; Woodruff-Pak & Disterhoft, 2008) Findings from human studies suggest that a trace interval of 500 ms impairs conditioning in medial temporal lobe amnesiacs (McGlinchey-Berroth et al, 1997) and activates the hippocampus more than delay conditioning in normal adults (Cheng et al, 2008) However, temporal lobe damage does not always impair conditioning with a 500 ms trace interval (Woodruff-Pak, 1993); whereas this damage appears to entirely prevent conditioning involving a 1000 ms trace interval (eg, Clark & Squire, 1998) Eyeblink conditioning emerges gradually over the course of development in both rodents (Stanton & Freeman, 2000) and humans (Ivkovich et al, 2000; Stanton et al, 2010) By 5 months post-term, normal human infants reach the same terminal level of conditioning as adults in the short delay procedure (Herbert et al, 2003) The aims of this study were (1) to replicate our previous findings of a fetal alcohol-related deficit on delay EBC seen in children at 5 years in a new sample of school-age, heavily alcohol exposed children; (2) to determine whether increased maturation between 5 and 9 years of age attenuates the alcohol effect of prenatal alcohol exposure on delay EBC; (3) to determine if trace conditioning is also impaired in children with fetal alcohol exposure and, if so, whether this task is more or less sensitive to this exposure than delay conditioning; (4) to examine whether retention of the delay CR after a 15-year period is altered by fetal alcohol exposure and whether alcohol exposure affects the rate of extinction of this response; (5) to determine if the effects of prenatal alcohol exposure on delay and trace conditioning are independent of the effects of this exposure on IQ; (6) to examine effects of prenatal alcohol exposure on precision of timing of the eyeblink CR; and (7) to determine whether extended training can result in conditioning in exposed children who do not initially meet learning criterion

Abstract: Section I: Overview Things you always wanted to know about conditioning, but were afraid to ask Todd R. Schachtman and Steve Reilly Section II: Applications to Clinical Pathology Fear extinction and emotional processing theory: A critical review Seth J. Gillihan and Edna Foa Fear Conditioning and Attention to Threat: An Integrative Approach to Understanding the Etiology of Anxiety Disorders Katherine Oehlberg and Susan Mineka Behavioral techniques to reduce relapse after exposure therapy: Applications of studies of experimental extinction Mario A. Laborda, Bridget L. McConnell, and Ralph R. Miller Learning and anxiety Peter F. Lovibond Trauma, learned helplessness, its neuroscience and implication for PTSD Vincent M. LoLordo and J. Bruce Overmier Abberant attentional processes in schizophrenia as reflected in latent inhibition data Robert E. Lubow Discrimination learning process in autism: spectrum disorders: A comparator theory Phil Reed Section III: Applications to Health and Addiction Conditioned Immunomodulation Jennifer L. Szczytkowski and Donald T. Lysle Learning, Expectancy and Behavioural Control: Implications for drug use M. Vogel-Sprott and Mark T. Fillmore Applications of Contemporary Learning Theory in the Treatment of Drug Abuse Danielle E. McCarthy, Timothy B. Baker, Haruka Minami, and Vivian Yeh Internal stimuli generated by abused substances: Role of Pavlovian conditioning and its implications for drug addiction Rick A. Bevins and Jennifer E. Murray Learning to eat: The influence of food cues on what, when and how much we eat Janet Polivy, C. Peter Herman, and Laura Girz Conditional analgesia, negative feedback & error correction Moriel Zelikowsky and Michael S. Fanselow Incentives in the modification and cessation of cigarette smoking Edwin B. Fisher, Leonard Green, Amanda L. Calvert, & Russell E. Glasgow Section IV: Applications to Cognition, Social Interaction and Motivation Social learning and connectionism Frank Van Overwalle Application of associative learning paradigms to clinically relevant individual differences in cognitive processing Teresa A. Treat, John L. Kruschke, Richard J. Viken, and Richard M. McFall A review of procedural knowledge about the mental process models of evaluative conditioning Jan De Houwer Instrumental and Pavlovian Conditioning Analogues of Familiar Social Processes Robert Ervin Cramer and Robert Frank Weiss The impact of social cognition on emotional learning from and about others: A neurobiological perspective Andreas Olsson Effects of Conditioning in Advertising Todd R. Schachtman, Jennifer Walker and Stephanie Fowler Applications of Pavlovian conditioning to sexual behavior and reproduction Michael Domjan and Chana K. Akins Hot and bothered: Classical conditioning of sexual incentives in humans Heather Hoffman

Abstract: During Pavlovian-to-instrumental transfer (PIT), learned Pavlovian cues significantly modulate ongoing instrumental actions. This phenomenon is suggested as a mechanism under which conditioned stimuli may lead to relapse in addicted populations. Following discriminative Pavlovian learning and instrumental conditioning with sucrose, one group of rats (naive) underwent electrophysiological recordings in the nucleus accumbens core and shell during a single PIT session. Other groups, following Pavlovian and instrumental conditioning, were subsequently trained to self-administer cocaine with nosepoke responses, or received yoked saline infusions and nosepoked for water rewards, and then performed PIT while electrophysiological recordings were taken in the nucleus accumbens. Behaviorally, although both naive and saline-treated groups showed increases in lever pressing during the conditioned stimulus cue, this effect was significantly enhanced in the cocaine-treated group. Neurons in the core and shell tracked these behavioral changes. In control animals, core neurons were significantly more likely to encode general information about cues, rewards and responses than those in the shell, and positively correlated with behavioral PIT performance, whereas PIT-specific encoding in the shell, but not core, tracked PIT performance. In contrast, following cocaine exposure, there was a significant increase in neural encoding of all task-relevant events that was selective to the shell. Given that cocaine exposure enhanced both behavior and shell-specific task encoding, these findings suggest that, whereas the core is important for acquiring the information about cues and response contingencies, the shell is important for using this information to guide and modulate behavior and is specifically affected following a history of cocaine self-administration.

Abstract: Classical conditioning of motor responses, such as the eyeblink response, is an experimental model of associative learning and of adaptive timing of movements. A conditioned blink will have its maximum amplitude near the expected onset of the unconditioned blink-eliciting stimulus and it adapts to changes in the interval between the conditioned and unconditioned stimuli. Previous studies have shown that an eyeblink conditioning protocol can make cerebellar Purkinje cells learn to pause in response to the conditioned stimulus. According to the cerebellar cortical conditioning model, this conditioned Purkinje cell response drives the overt blink. If so, the model predicts that the temporal properties of the Purkinje cell response reflect the overt behaviour. To test this prediction, in vivo recordings of Purkinje cell activity were performed in decerebrate ferrets during conditioning, using direct stimulation of cerebellar mossy and climbing fibre afferents as conditioned and unconditioned stimuli. The results show that Purkinje cells not only develop a change in responsiveness to the conditioned stimulus. They also learn a particular temporal response profile where the timing, not only of onset and maximum but also of offset, is determined by the temporal interval between the conditioned and unconditioned stimuli.

Abstract: Individuals weigh information about both rewarding and aversive stimuli to make adaptive decisions. Most studies of the orbitofrontal cortex (OFC), an area where appetitive and aversive neural subsystems might interact, have focused only on reward. Using a classical conditioning task where novel stimuli are paired with a reward or an aversive air puff, we discovered that two groups of orbitofrontal neurons respond preferentially to conditioned stimuli associated with rewarding and aversive outcomes; however, information about appetitive and aversive stimuli converges on individual neurons from both populations. Therefore, neurons in the OFC might participate in appetitive and aversive networks that track the motivational significance of stimuli even when they vary in valence and sensory modality. Further, we show that these networks, which also extend to the amygdala, exhibit different rates of change during reversal learning. Thus, although both networks represent appetitive and aversive associations, their distinct temporal dynamics might indicate different roles in learning processes.

Abstract: We studied the interactions between short- and long-term plastic changes taking place during the acquisition of a classical eyeblink conditioning and following high-frequency stimulation (HFS) of the reuniens nucleus in behaving mice. Synaptic changes in strength were studied at the reuniens-medial prefrontal cortex (mPFC) and the reuniens-CA1 synapses. Input/output curves and a paired-pulse study enabled determining the functional capabilities of the two synapses and the optimal intensities to be applied at the reuniens nucleus during classical eyeblink conditioning and for HFS applied to the reuniens nucleus. Animals were conditioned using a trace paradigm, with a tone as conditioned stimulus (CS) and an electric shock to the trigeminal nerve as unconditioned stimulus (US). A single pulse was presented to the reuniens nucleus to evoke field EPSPs (fEPSPs) in mPFC and CA1 areas during the CS-US interval. No significant changes in synaptic strength were observed at the reuniens-mPFC and reuniens-CA1 synapses during the acquisition of eyelid conditioned responses (CRs). Two successive HFS sessions carried out during the first two conditioning days decreased the percentage of CRs, without evoking any long-term potentiation (LTP) at the recording sites. HFS of the reuniens nucleus also prevented the proper acquisition of an object discrimination task. A subsequent study revealed that HFS of the reuniens nucleus evoked a significant decrease of paired-pulse facilitation. In conclusion, reuniens nucleus projections to prefrontal and hippocampal circuits seem to participate in the acquisition of associative learning through a mechanism that does not required the development of LTP.

Abstract: Locusts can learn associations between olfactory stimuli and food rewards, and use the acquired memories to choose between foods according to their nutrient requirements. They are a model system for both the study of olfactory coding and insect nutritional regulation. Previous studies have used operant paradigms for conditioning freely moving locusts, restricting the study of the neural mechanisms underlying the acquisition of olfactory memories, which requires restrained preparations for electrophysiological recordings. Here we present two complementary paradigms for the classical conditioning of olfactory memories in restrained desert locusts (Schistocerca gregaria). These paradigms allow precise experimental control over the parameters influencing learning. The first paradigm is based on classical (Pavlovian) appetitive conditioning. We show that opening of the maxillary palps can be used as a measure of memory acquisition. Maxillary palp opening in response to odour presentation is significantly higher in locusts trained with paired presentation of an odour and a food reward than in locusts trained either with unpaired presentation of food and odour or the odour alone. The memory formed by this conditioning paradigm lasts for at least 24 h. In the second paradigm, we show that classical conditioning of an odour memory in restrained locusts influences their decisions in a subsequent operant task. When locusts that have been trained to associate an odour with a food reward are placed in a Y-maze, they choose the arm containing that odour significantly more often than naive locusts. A single conditioning trial is sufficient to induce a significant bias for that odour for up to 4 h. Multiple- and block-trial training induce a significant bias that lasts at least 24 h. Thus, locusts are capable of forming appetitive olfactory memories in classical conditioning paradigms and can use these memories to modify their decisions.

Abstract: Associative conditioning in Drosophila melanogaster has been well documented for several decades. However, most studies report only simple associations of conditioned stimuli (CS, e.g., odor) with unconditioned stimuli (US, e.g., electric shock) to measure learning or establish memory. Here we describe a straightforward second-order conditioning (SOC) protocol that further demonstrates the flexibility of fly behavior. In SOC, a previously conditioned stimulus (CS1) is used as reinforcement for a second conditioned stimulus (CS2) in associative learning. This higher-order context presents an opportunity for reassessing the roles of known learning and memory genes and neuronal networks in a new behavioral paradigm.

Abstract: Classical conditioning of a motor response such as eyeblink is associated with the development of a pause in cerebellar Purkinje cell firing that is an important driver of the overt response. This conditioned Purkinje cell response is adaptively timed and has a specific temporal profile that probably explains the time course of the overt behavior. It is generally assumed that the temporal properties of the conditioned Purkinje cell response are determined by the temporal pattern of the parallel fiber impulses generated by the conditioned stimulus at the time of the conditioned response. We show here in the decerebrate ferret preparation that a very brief conditioned stimulus, consisting of only one or two impulses in the mossy fibers, can be sufficient to elicit a full conditioned Purkinje cell response with normal time course. The finding suggests that parallel fiber input to the Purkinje cell influences the firing rate several hundred milliseconds later. It poses a serious challenge to the standard view of the role of parallel fiber impulses in response timing.

Abstract: After having demonstrated that blood-sucking bugs are able to associate a behaviourally neutral odour (L-lactic acid) with positive reinforcement (i.e. appetitive conditioning) in the first part of this study, we tested whether these insects were also able to associate the same odour with a negative reinforcement (i.e. aversive conditioning). Learned aversion to host odours has been repeatedly suggested as a determinant for the distribution of disease vectors among host populations. Nevertheless, no experimental evidence has been obtained so far. Adapting a classical conditioning approach to our haematophagous model, we trained larvae of Rhodnius prolixus to associate L-lactic acid, an odour perceived by bugs but behaviourally neutral when presented alone, with a mechanical perturbation (i.e. negative reinforcement). Naive bugs and bugs exposed to CS, punishment, or CS and punishment without contingency remained indifferent to the presence of an air stream loaded with L-lactic acid (random orientation on a locomotion compensator), whereas the groups previously exposed to the contingency CS-punishment were significantly repelled by L-lactic acid. In a companion paper, the opposite, i.e. attraction, was induced in bugs exposed to the contingency of the same odour with a positive reinforcement. These constitute the first pieces of evidence of olfactory conditioning in triatomine bugs and the first demonstration that the same host odour can be used by insects that are disease vectors to learn to recognize either a host to feed on or a potentially defensive one. The orientation mechanism during repulsion is also discussed in light of our results.

Abstract: Akin to other physiological responses, the immune system can be modified, via Pavlovian or behavioral conditioning. It is unknown, however, whether and to what extent learned immune responses can be repeatedly recalled over time. Here we demonstrate in both rats and humans that repeated contingent pairing of a novel taste (conditioned stimulus, CS) together with the immunosuppressive drug cyclosporine A as unconditioned stimulus (US) leads to the acquisition of a learned immunosuppression. Sole presentation of the CS caused a significant inhibition of interleukin (IL)-2 and interferon (IFN)-γ production by rat splenic T cells and human peripheral T lymphocytes, closely mimicking the effect of the drug. More importantly, a comparable suppression of cytokine production was also observed after a second, unreinforced exposure to the CS that was separated from the first evocation by an interval of 6 (rats) or 11 (humans) days, respectively. Together, our findings demonstrate that a learned immunosuppression can be repeatedly recalled in both animals and humans, which is an important prerequisite for the implementation of conditioning paradigms as supportive therapy.

Abstract: Vision is an ancient sense essential for various aspects of animal behavior. Visual information not only leads to immediate, temporary, and rapid behavioral responses but also has lasting effects. Naive behavioral responses to light are not always identical but can be altered based on positive or negative experience-a process defined as visual learning. In this study, Drosophila larvae were used as a simple model to study visual classical conditioning. We show that larvae are able to associate positive or negative cues with either light or darkness, thus changing their native light-preference. This effect can be robustly provoked through gustatory stimuli and electric shock. We further show that light can not only be used as a conditioned stimulus but also as an unconditioned stimulus, as punishment in the olfactory classical conditioning procedure, possibly forming two different kinds of memories. Our findings show that even though larvae show a strong naive response when exposed to light, the animals display a comparably large repertoire of visual memories that can be formed. Therefore, our study provides an impacting entry point into the genetic dissection of the neuronal circuit that underlies different types of visual learning.

Abstract: Current models that account for attentional processes in anxiety have proposed that high-trait anxious individuals are characterized by a hypervigilant-avoidant pattern of attentional biases to threat. We adopted a laboratory conditioning procedure to induce concomitant hypervigilance and avoidance to threat, emphasizing a putative relationship between lower-level reactive and upper-level controlled attentional mechanisms as the core account of attentional processes involved in the development and maintenance of anxiety. Eighty high- and low-trait anxious participants underwent Pavlovian conditioning to a human face. Eye tracking was used to monitor attentional changes to the conditioned stimulus (CS+) face and the neutral stimulus (CS-) face, presented at 200, 500, and 800 ms durations. The high-anxious participants developed the expected attentional bias toward the CS+ at 200 ms presentation time and attentional avoidance at 500 and 800 ms durations. Hypervigilance to aversive stimuli at 200 ms and later avoidance to the same stimuli at 500 and 800 ms were associated with higher levels of galvanic skin conductance to the CS+. The low-anxious individuals developed the opposite attentional pattern with an initial tendency to orient attention away from the aversive stimuli in the 200 ms condition and to orient attention toward aversive stimuli in the remaining time. The differential modulation between hypervigilance and avoidance elicited in the two groups by the conditioning procedure suggests that vulnerability to anxiety is characterized by a latent relationship between diverse attentional mechanisms. Within this relationship, hypervigilance and avoidance to threat operate at different stages of information processing suggesting fuzzy boundaries between early reactive and later-strategic processing of threat.

Abstract: There has been considerable recent interest in comparing the circuit and monoamine-based mechanisms of aversive and reward-associative conditioning in a number of vertebrate and invertebrate model systems. The mollusc Lymnaea stagnalis provides a unique opportunity to explore changes in the neural and chemical pathways underlying these two different types of conditioning as its feeding circuitry has been thoroughly characterised. Animals can learn after a single trial to associate the same CS (amyl acetate) either with a punishment (quinine) or reward (sucrose), showing either a reduced or an elevated feeding response, respectively, to the CS. We previously showed that reward conditioning strengthened the direct excitatory pathway from the lips to the feeding central pattern generator in the buccal ganglia through the activation of feeding interneurons in the cerebral ganglia. Now we demonstrate that aversive conditioning enhances the strength of a different inhibitory pathway that suppresses feeding but has no effect on the excitatory pathway. Here we show that consolidation of long-term memory (LTM) in reward conditioning depends on dopamine but not octopamine. In contrast, aversive LTM depends on octopamine but not dopamine. Octopamine is the invertebrate equivalent of noradrenalin, so these results on the monoamine dependence of reward and aversive conditioning in Lymnaea resemble, at the transmitter receptor level, those in mammals but are the opposite of those in another invertebrate group, the insects.

Abstract: Trace eyeblink classical conditioning (tEBCC) can be accelerated by making training trials contingent on the naturally generated hippocampal 3- to 7-Hz theta rhythm. However, it is not well-underst...

Abstract: Associations between drugs of abuse and cues facilitate the acquisition and maintenance of addictive behaviors. Although significant research has been done to elucidate the role that simple discriminative or discrete conditioned stimuli (e.g., a tone or a light) play in addiction, less is known about complex environmental cues. The purpose of the present study was to examine the role of a musical conditioned stimulus by assessing locomotor activity and in vivo microdialysis. Two groups of rats were given non-contingent injections of methamphetamine (1.0 mg/kg) or vehicle and placed in standard conditioning chambers. During these conditioning sessions both groups were exposed to a continuous conditioned stimulus, in the form of a musical selection ("Four" by Miles Davis) played repeatedly for 90 min. After seven consecutive conditioning days subjects were given one day of rest, and subsequently tested for locomotor activity or dopamine release in the absence of drugs while the musical conditioned stimulus was continually present. The brain regions examined included the basolateral amygdala, nucleus accumbens, and prefrontal cortex. The results show that music is an effective contextual conditioned stimulus, significantly increasing locomotor activity after repeated association with methamphetamine. Furthermore, this musical conditioned stimulus significantly increased extracellular dopamine levels in the basolateral amygdala and nucleus accumbens. These findings support other evidence showing the importance of these brain regions in conditioned learning paradigms, and demonstrate that music is an effective conditioned stimulus warranting further investigation.