Classical Conditioning Experiments Research Articles

Bio-inspired artificial heterosynapse based on carbon nanotubes memtransistor with dynamically tunable analog switching behavior

The swift advancement of artificial intelligence necessitates the exigency for a proficient information processing system. Taking inspiration from the intricate synapses of the human brain, we have crafted an artificial heterosynapse utilizing carbon nanotube (CNT) memtransistors. The multi-terminal heterosynaptic plasticity of CNTs memtransistor could be effectively modulated by gate voltage or drain voltage, which resembles the biological synapses affected by external neuromodulators. The artificial synapse skillfully replicates neuromorphic functionalities in response to pulse stimuli. This enables tunable analog switching behavior, multiple memory states, and complex neuromorphic learning. Furthermore, the Pavlovian classical conditioning experiments were conducted utilizing the synaptic device to achieve associative learning. The introduction of the CNTs memtransistor will propel the advancement of neuromorphic device technology and unlock novel opportunities for designing learning schemes with an additional degree of freedom.

Energy-efficient flexible photoelectric device with 2D/0D hybrid structure for bio-inspired artificial heterosynapse application

The booming artificial intelligence has led to an urgent demand for high-efficient information processing systems. Inspired by the interconnected synapses in human brain, we constructed a novel low-dimensional flexible hybrid photoelectric-modulated artificial heterosynapse with sub-femtojoule energy consumption (0.58 fJ/spike in long-term potentiation (LTP) and 0.86 fJ/spike in long-term depression (LTD)) and ultrafast response (50 ns), which is 10 5 folds faster than human brain (10 ms). The device synergistically utilizes the remarkable photoelectric properties of a 2D MoSSe channel and a 0D BPQD trap layer to achieve a better computing architecture. The artificial synapse successfully emulates neuromorphic functions under both electric and light stimuli. More importantly, the multi-terminal heterosynaptic plasticity can be modulated effectively by three factors in a cumulative/subtractive way, resembling biological synapses affected by an external neuromodulator, enabling higher order LTP correlations (percentage of increase is ~203% compared with electric modulation) and multiple memory states. The performance of the device was unaffected by substrate bending, indicating the robust stability and high flexibility under mechanical strains. Moreover, the Pavlov’s dog classical conditioning experiments were performed to realize associative learning with the synaptic device. These results highlight a new approach for constructing highly efficient wearable neuromorphic computing systems based on mixed low-dimensional structures. • The 2D MoSSe/0D BPQDs hybrid structure for artificial heterosynapse was reported firstly, and the device exhibits reliable flexibility. • Ultralow power consumption of 0.58 fJ/spike in long-term-potentiation. • Ultrafast programing and erasing speed of 50 ns in flexible neuron-transistor. • By virtue of heterosynaptic characteristics, the modulation range of conductance could be enlarged to ~203% compared with pure-electric modulation.

Brain-inspired classical conditioning model.

SummaryClassical conditioning plays a critical role in the learning process of biological brains, and many computational models have been built to reproduce the related classical experiments. However, these models can reproduce and explain only a limited range of typical phenomena in classical conditioning. Based on existing biological findings concerning classical conditioning, we build a brain-inspired classical conditioning (BICC) model. Compared with other computational models, our BICC model can reproduce as many as 15 classical experiments, explaining a broader set of findings than other models have, and offers better computational explainability for both the experimental phenomena and the biological mechanisms of classical conditioning. Finally, we validate our theoretical model on a humanoid robot in three classical conditioning experiments (acquisition, extinction, and reacquisition) and a speed generalization experiment, and the results show that our model is computationally feasible as a foundation for brain-inspired robot classical conditioning.

Consistent individual differences in associative learning speed are not linked to boldness in female Atlantic mollies.

Recent studies on consistent individual differences in behavioural tendencies (animal personality) raised the question of whether individual differences in cognitive abilities can be linked to certain personality types. We tested female Atlantic mollies (Poecilia mexicana) in two different classical conditioning experiments. For the first time, we provide evidence for highly consistent individual differences in associative learning speed in fish. We characterized the same individuals for boldness in two experimental situations (latency to emerge from shelter and freezing time after a simulated predator attack) and found high behavioural repeatability. When we tested for a potential correlation between associative learning speed and boldness, however, there was no evidence for a link between them. Our study design included several steps to avoid typical pitfalls of disadvantaging shy individuals during learning tests. We caution that other experimental studies may have suffered from erroneous interpretations due to a more cautious coping style of shy individuals in the respective setup used to assess learning.

Prepared stimuli enhance aversive learning without weakening the impact of verbal instructions.

Fear-relevant stimuli such as snakes and spiders are thought to capture attention due to evolutionary significance. Classical conditioning experiments indicate that these stimuli accelerate learning, while instructed extinction experiments suggest they may be less responsive to instructions. We manipulated stimulus type during instructed aversive reversal learning and used quantitative modeling to simultaneously test both hypotheses. Skin conductance reversed immediately upon instruction in both groups. However, fear-relevant stimuli enhanced dynamic learning, as measured by higher learning rates in participants conditioned with images of snakes and spiders. Results are consistent with findings that dissociable neural pathways underlie feedback-driven and instructed aversive learning.

Modeling the neural substrates of learning through conditioning: A two-phased model

How animals and humans obtain relevant representations of the environment for their survival is not fully understood. Classical conditioning experiments have sometimes helped identify when those representations are learned. We review the literature that highlights the roles of the amygdala during classical conditioning, including the association of emotional responses between conditioned stimuli (CS) and unconditioned stimuli (US) and stimuli-induced synaptic plasticity in sensory areas. The particular connectivity from both cortical and subcortical areas to the amygdala and from the amygdala toward the main brain areas, releasing plasticity-inducing neurotransmitters, suggests that the role of the amygdala goes beyond the formation of emotional memories toward the encoding of valence (e.g., the positive or negative emotional value of a stimulus) or relevance. This particular architecture positions the amygdala as a driver of motivation and sensory modulation. We suggest that amygdalar CS-US associations indirectly attribute to the CS the capacity to regulate synaptic-plasticity-inducing neurotransmitters in the brain. We present a model of cholinergic modulation of the sensory cortex that addresses these roles. This model is a first step toward a two-phased learning theory, with sensory learning scaffolding associative learning. This model predicts that a cascade of iteratively learned US-CS and CS-CS associations found in daily life could help fine-tune relevant perceptual and behavioral skills.

Neural representation of a spatial odor memory in the honeybee mushroom body

Insects make use of lateralized olfactory information from their left and right antennae. Honeybees can learn to distinguish side-specific odor cues in classical conditioning experiments, i.e. they associate a specific stimulus combination of odor identity and spatial location (left or right) with the reward [1]. This requires inter-hemispheric transfer of lateralized information and a side-specific odor memory. Mushroom body (MB) output neurons, the so-called extrinsic neurons (ENs), make inter-hemispheric connections between the two MBs and are thus candidates for the inter-hemispheric transfer of lateralized stimulus information. We could show previously that ENs in the honeybee undergo plastic changes in classical conditioning [2]. Here, we investigate neuronal plasticity in ENs of the honeybee in a sides-specific learning paradigm. We performed multiple single-unit recordings from ENs of one MB. Prior to conditioning (PRE) each bee was repeatedly presented with two different odors on the two antennae separately. During acquisition one of these odors was repeatedly presented to the antenna contralateral to the recording side (CS+) and paired with a sugar reward, while the other odor was presented without reward (differential conditioning). Three hours after training (POST) we repeated the initial protocol presenting each of the two odors repeatedly to each of the antennae. In the behavioral test the bees distinguished the CS+ stimulus configuration of odor and side from the other three stimulus combinations. At the neuronal level we found clear and distinct odor representations in the EN population before training (PRE) only when stimulated on the antenna ipsilateral to the recording side. However, no odor responses were measured in any of the ENs when stimulated at the contralateral antenna. This picture changed drastically after training (POST). Now, the rewarded stimulus combination (CS+) resulted in a strong population response pattern. The population code for the CS+ configuration was clearly distinct from all three other stimulus configurations. Quantification of the temporal response latencies showed that the ENs encode an odor approximately within 75ms for ipsilateral stimulation. Odor representation was delayed by about 60ms for a contralateral stimulation. We discuss two alternative explanations for this temporal delay. We hypothesized previously that ENs at the MB output encode the experience-dependent value of a particular stimulus [2-4]. Our results here provide additional evidence for this hypothesis. A representation of the rewarded stimulus combination (CS+) of a particular odor and its spatial location (left or right) develops only due to reward conditioning. Before learning, only ipsilateral odor information was represented.

Drosophila adult olfactory shock learning.

Drosophila have been used in classical conditioning experiments for over 40 years, thus greatly facilitating our understanding of memory, including the elucidation of the molecular mechanisms involved in cognitive diseases1-7. Learning and memory can be assayed in larvae to study the effect of neurodevelopmental genes8-10 and in flies to measure the contribution of adult plasticity genes1-7. Furthermore, the short lifespan of Drosophila facilitates the analysis of genes mediating age-related memory impairment5,11-13. The availability of many inducible promoters that subdivide the Drosophila nervous system makes it possible to determine when and where a gene of interest is required for normal memory as well as relay of different aspects of the reinforcement signal3,4,14,16.Studying memory in adult Drosophila allows for a detailed analysis of the behavior and circuitry involved and a measurement of long-term memory15-17. The length of the adult stage accommodates longer-term genetic, behavioral, dietary and pharmacological manipulations of memory, in addition to determining the effect of aging and neurodegenerative disease on memory3-6,11-13,15-21.Classical conditioning is induced by the simultaneous presentation of a neutral odor cue (conditioned stimulus, CS+) and a reinforcement stimulus, e.g., an electric shock or sucrose, (unconditioned stimulus, US), that become associated with one another by the animal1,16. A second conditioned stimulus (CS-) is subsequently presented without the US. During the testing phase, Drosophila are simultaneously presented with CS+ and CS- odors. After the Drosophila are provided time to choose between the odors, the distribution of the animals is recorded. This procedure allows associative aversive or appetitive conditioning to be reliably measured without a bias introduced by the innate preference for either of the conditioned stimuli. Various control experiments are also performed to test whether all genotypes respond normally to odor and reinforcement alone.

<em>Drosophila</em> Adult Olfactory Shock Learning

Drosophila have been used in classical conditioning experiments for over 40 years, thus greatly facilitating our understanding of memory, including the elucidation of the molecular mechanisms involved in cognitive diseases1-7. Learning and memory can be assayed in larvae to study the effect of neurodevelopmental genes8-10 and in flies to measure the contribution of adult plasticity genes1-7. Furthermore, the short lifespan of Drosophila facilitates the analysis of genes mediating age-related memory impairment5,11-13. The availability of many inducible promoters that subdivide the Drosophila nervous system makes it possible to determine when and where a gene of interest is required for normal memory as well as relay of different aspects of the reinforcement signal3,4,14,16. Studying memory in adult Drosophila allows for a detailed analysis of the behavior and circuitry involved and a measurement of long-term memory15-17. The length of the adult stage accommodates longer-term genetic, behavioral, dietary and pharmacological manipulations of memory, in addition to determining the effect of aging and neurodegenerative disease on memory3-6,11-13,15-21. Classical conditioning is induced by the simultaneous presentation of a neutral odor cue (conditioned stimulus, CS+) and a reinforcement stimulus, e.g., an electric shock or sucrose, (unconditioned stimulus, US), that become associated with one another by the animal1,16. A second conditioned stimulus (CS-) is subsequently presented without the US. During the testing phase, Drosophila are simultaneously presented with CS+ and CS- odors. After the Drosophila are provided time to choose between the odors, the distribution of the animals is recorded. This procedure allows associative aversive or appetitive conditioning to be reliably measured without a bias introduced by the innate preference for either of the conditioned stimuli. Various control experiments are also performed to test whether all genotypes respond normally to odor and reinforcement alone.

Galantamine reverses scopolamine-induced behavioral alterations in Dugesia tigrina

In planaria (Dugesia tigrina), scopolamine, a nonselective muscarinic receptor antagonist, induced distinct behaviors of attenuated motility and C-like hyperactivity. Planarian locomotor velocity (pLMV) displayed a dose-dependent negative correlation with scopolamine concentrations from 0.001 to 1.0 mM, and a further increase in scopolamine concentration to 2.25 mM did not further decrease pLMV. Planarian hyperactivity counts was dose-dependently increased following pretreatment with scopolamine concentrations from 0.001 to 0.5 mM and then decreased for scopolamine concentrations ≥ 1 mM. Planarian learning and memory investigated using classical Pavlovian conditioning experiments demonstrated that scopolamine (1 mM) negatively influenced associative learning indicated by a significant decrease in % positive behaviors from 86 % (control) to 14 % (1 mM scopolamine) and similarly altered memory retention, which is indicated by a decrease in % positive behaviors from 69 % (control) to 27 % (1 mM scopolamine). Galantamine demonstrated a complex behavior in planarian motility experiments since co-application of low concentrations of galantamine (0.001 and 0.01 mM) protected planaria against 1 mM scopolamine-induced motility impairments; however, pLMV was significantly decreased when planaria were tested in the presence of 0.1 mM galantamine alone. Effects of co-treatment of scopolamine and galantamine on memory retention in planaria via classical Pavlovian conditioning experiments showed that galantamine (0.01 mM) partially reversed scopolamine (1 mM)-induced memory deficits in planaria as the % positive behaviors increased from 27 to 63 %. The results demonstrate, for the first time in planaria, scopolamine's effects in causing learning and memory impairments and galantamine's ability in reversing scopolamine-induced memory impairments.

Beyond Organic Aetiology: Exploring A Psychocognitive Approach To Gastric Ulceration

Pavlov's classical conditioning experiments brought to the fore how stimuli of purely psychogenic nature mediate and affect cognitive state, hence, shaping physiologic functions. Against this background, I seek to understand how the triad of the brain, the mind and our human experiences (in the context of disease) interact. I attempt a systematic explication of how this interaction may occur in the onset of gastric ulceration. On that note, I argue that a valid psychocognitive frame of reference offers creative insights into how non-phar- macological means may be employed in the clinical palliation of forms of non-organic gastric ulcers.

Exploring a latent cause theory of classical conditioning

We frame behavior in classical conditioning experiments as the product of normative statistical inference. According to this theory, animals learn an internal model of their environment from experience. The basic building blocks of this internal model are latent causes-explanatory constructs inferred by the animal that partition observations into coherent clusters. Generalization of conditioned responding from one cue to another arises from the animal's inference that the cues were generated by the same latent cause. Through a wide range of simulations, we demonstrate where the theory succeeds and where it fails as a general account of classical conditioning.

A Distinct Set ofDrosophilaBrain Neurons Required for Neurofibromatosis Type 1-Dependent Learning and Memory

Nonspecific cognitive impairments are one of the many manifestations of neurofibromatosis type 1 (NF1). A learning phenotype is also present in Drosophila melanogaster that lack a functional neurofibromin gene (nf1). Multiple studies have indicated that Nf1-dependent learning in Drosophila involves the cAMP pathway, including the demonstration of a genetic interaction between Nf1 and the rutabaga-encoded adenylyl cyclase (Rut-AC). Olfactory classical conditioning experiments have previously demonstrated a requirement for Rut-AC activity and downstream cAMP pathway signaling in neurons of the mushroom bodies. However, Nf1 expression in adult mushroom body neurons has not been observed. Here, we address this discrepancy by demonstrating (1) that Rut-AC is required for the acquisition and stability of olfactory memories, whereas Nf1 is only required for acquisition, (2) that expression of nf1 RNA can be detected in the cell bodies of mushroom body neurons, and (3) that expression of an nf1 transgene only in the alpha/beta subset of mushroom body neurons is sufficient to restore both protein synthesis-independent and protein synthesis-dependent memory. Our observations indicate that memory-related functions of Rut-AC are both Nf1-dependent and -independent, that Nf1 mediates the formation of two distinct memory components within a single neuron population, and that our understanding of Nf1 function in memory processes may be dissected from its role in other brain functions by specifically studying the alpha/beta mushroom body neurons.

Timing using temporal context

We present a memory model that explicitly constructs and stores the temporal information about when a stimulus was encountered in the past. The temporal information is constructed from a set of temporal context vectors adapted from the temporal context model (TCM). These vectors are leaky integrators that could be constructed from a population of persistently firing cells. An array of temporal context vectors with different decay rates calculates the Laplace transform of real time events. Simple bands of feedforward excitatory and inhibitory connections from these temporal context vectors enable another population of cells, timing cells. These timing cells approximately reconstruct the entire temporal history of past events. The temporal representation of events farther in the past is less accurate than for more recent events. This history-reconstruction procedure, which we refer to as timing from inverse Laplace transform (TILT), displays a scalar property with respect to the accuracy of reconstruction. When incorporated into a simple associative memory framework, we show that TILT predicts well-timed peak responses and the Weber law property, like that observed in interval timing tasks and classical conditioning experiments.

A computational model of associative learning and chemotaxis in the nematode worm C. elegans

The nematode worm C. elegans is an exciting model system for experimentalists and modelers alike. It has a relatively small nervous system, made up of just 302 neurons in the adult hermaphrodite, that has been mapped in detail using serial section electron microscopy. Despite the simplicity of its nervous system C. elegans displays a range of interesting behaviors. This includes thermo- and chemotaxis and the modulation of locomotion strategies in response to the presence of food. In chemotaxis C. elegans will move up or down a chemical gradient dependent on whether the chemical acts as an attractant or repellent. It does this in two distinct ways, first by gradually steering left or right until the worm points up or down the gradient and second by modulating the probability of initiating a sharp series of turns (known as a piroeutte) along with the final orientation of the worm after the pirouette has finished. Experimental work has shown that the chemotaxis response is dynamic and that the degree of influence a particular chemical has on navigation can be changed, or even reversed depending on experience. Changes are reversible, specific to the chemical in question, and can be generated by classical conditioning experiments. All of these are hallmarks of associative learning, a sophisticated process that requires integration of multiple signals to produce a coordinated change in a behavioral response. Despite the wealth of experimental data on learning in chemotaxis in C. elegans, comparatively little is known about how the known circuitry of C. elegans carries out the computations that underlie it. Even less is known about how that circuitry changes during associative learning. Here, we focus on the worm's chemotaxis and the ability of C. elegans to learn associations between salt (NaCl) concentrations and food. We draw upon existing experimental data from a variety of sources including electrophysiological and anatomical data to construct a simplified NaCl chemotaxis circuit in C. elegans. This circuit consists of the left and right ASE amphid sensory neurons, which comprise the dominant NaCl sensation pathway in C. elegans, eight pairs of interneurons, and ten head motor neurons. Where possible the properties of individual neurons are constrained by electrophysiological and calcium imaging data. We next define a set of experimentally observed behaviors we wish to reproduce, including gentle turning, modulation of pirouette frequency, control of final orientation following a pirouette, and associative learning. In particular, we are interested in the alteration in behavioral response to NaCl that arises due to the pairing of high concentrations of NaCl with food or starvation. We use this to derive a family of model networks with specific synaptic polarities, time scales of neuronal responses, and intrinsic neuronal properties that have the capacity to generate the specified set of behaviors. We implement one of these models and record the behaviour of model worms that are placed in a variety of simulated environments. We observe qualitatively realistic chemotaxis behavior and adaptation and demonstrate that our model is robust and tolerant to noise. Our proposed chemotaxis circuit leads to a number of distinct predictions that could be used to test the model experimentally. This includes postulating the computational role of each neuron in the network and the locus and nature of the plasticity underpinning the experimentally observed associative learning. Our model also suggests that this plasticity be expressed not by changes in synaptic strength but by changes in the sensory neurons themselves. Thus, contrary to the prevailing view in the C. elegans community, plasticity in our model of chemotaxis is expressed at a neuronal rather than synaptic level. C. elegans offers a unique opportunity to push the boundaries of systems neuroscience. The ability to model a neuronal circuit in such detail is a remarkable opportunity to study associative learning in an animal displaying a sophisticated set of behaviors and nontrivial learning. A biologically grounded model of behavior and learning in C. elegans has great potential to offer detailed and integrated understanding of sensory processing, synaptic plasticity and associative learning. Lessons learned from such models can be applied to other sensory and sensorimotor modalities in the worm with the eventual goal of producing an integrated model of the worm's sensorimotor system. We believe that theoretical insights gained from this endeavour will be invaluable in our study of larger, more complex nervous systems.

Classical conditioning of autonomic fear responses is independent of contingency awareness.

The role of contingency awareness in classical conditioning experiments using human subjects is currently under debate. This study took a novel approach to manipulating contingency awareness in a differential Pavlovian conditioning paradigm. Complex sine wave gratings were used as visual conditional stimuli (CS). By manipulating the fundamental spatial frequency of the displays, we were able to construct pairs of stimuli that varied in discriminability. One group of subjects was given an "easy" discrimination, and another was exposed to a "difficult" CS+ and CS-. A 3rd group was exposed to a stimulus that was paired with the unconditional stimulus (UCS) 50% of the time and served as a control. Skin conductance response (SCR) and continuous UCS expectancy data were measured concurrently throughout the experiment. Differential UCS expectancy was found only in the easy discrimination group. Differential SCRs were found in the easy discrimination group as well as in the difficult discrimination group, but not in the 50% contingency control. The difficult discrimination group did not exhibit differential UCS expectancy but did show clear differential SCR. These observations support a dual process interpretation of classical conditioning whereby conditioning on an implicit level can occur without explicit knowledge about the contingencies. The role of contingency awareness in classical conditioning experiments using human subjects is currently under debate. This study took a novel approach to manipulating contingency awareness in a differential Pavlovian conditioning paradigm. Complex sine wave gratings were used as visual conditional stimuli (CS). By manipulating the fundamental spatial frequency of the displays, we were able to construct pairs of stimuli that varied in discriminability. One group of subjects was given an "easy" discrimination, and another was exposed to a "difficult" CS+ and CS-. A 3rd group was exposed to a stimulus that was paired with the unconditional stimulus (UCS) 50% of the time and served as a control. Skin conductance response (SCR) and continuous UCS expectancy data were measured concurrently throughout the experiment. Differential UCS expectancy was found only in the easy discrimination group. Differential SCRs were found in the easy discrimination group as well as in the difficult discrimination group, but not in the 50% contingency control. The difficult discrimination group did not exhibit differential UCS expectancy but did show clear differential SCR. These observations support a dual process interpretation of classical conditioning whereby conditioning on an implicit level can occur without explicit knowledge about the contingencies.

Associative and non-associative blinking in classically conditioned adult rats

Over the last several years, a growing number of investigators have begun using the rat in classical eyeblink conditioning experiments, yet relatively few parametric studies have been done to examine the nature of conditioning in this species. We report here a parametric analysis of classical eyeblink conditioning in the adult rat using two conditioned stimulus (CS) modalities (light or tone) and three interstimulus intervals (ISI; 280, 580, or 880 ms). Rats trained at the shortest ISI generated the highest percentage of conditioned eyeblink responses (CRs) by the end of training. At the two longer ISIs, rats trained with the tone CS produced unusually high CR percentages over the first few acquisition sessions, relative to rats trained with the light CS. Experiment 2 assessed non-associative blink rates in response to presentations of the light or tone, in the absence of the US, at the same ISI durations used in paired conditioning. Significantly more blinks occurred with longer than shorter duration lights or tones. A higher blink rate was also recorded at all three durations during the early tone-alone sessions. The results suggest that early in classical eyeblink conditioning, rats trained with a tone CS may emit a high number of non-associative blinks, thereby inflating the CR frequency reported at this stage of training.

Mushroom-bodies regulate habit formation in Drosophila

AbstractOur past experience is one of the primary sources of information when faced with a choice. We ask ourselves: "what will happen if I do this?"Accurately predicting the consequences of our actions is usually modeled by operant (instrumental) learning experiments. These types of experiments are often contrasted with classical (Pavlovian) conditioning experiments in a dichotomy. And indeed, different brain circuits mediate the acquisition of skills and habits (via operant/instrumental learning) and the acquisition of facts (via classical/Pavlovian learning). However, realistic learning situations always comprise interactions of skill- and fact-learning components (composite learning). Fixed flying Drosophila melanogaster at the torque meter provide one of the very few systems where the relationship of operant and classical predictors in composite learning can be studied with sufficient rigor. The latest experiments show that the textbook operant/classical dichotomy is misleading and that instead composite learning consists of multiple interacting memory systems. These interactions between predictive stimuli (classical component) and goal-directed actions (operant component) make composite conditioning more effective than the operant and classical components alone (learning-by-doing, generation effect). Rutabaga (rut) mutants are impaired in learning about the (classical) stimuli, but show improved (operant) behavior learning. This is the first evidence that operant and classical conditioning differ not only at the circuit, but also at the molecular level. The interaction between operant and classical components is reciprocal and hierarchical, such that the classical suppresses the operant component. Experiments with transgenic flies demonstrate that this suppression of operant learning is mediated by the mushroom-bodies and serves to ensure that the classical memories can be generalized for access by other behaviors. Extended training can overcome this suppression and transforms goal-directed actions into habitual responses. This interaction leads to efficient learning, enables generalization and prevents premature habit-formation.

IDENTIFICATION OF LINOTTE, A NEW GENE AFFECTING LEARNING AND MEMORY IN DROSOPHILA MELANOGASTER

We describe the identification of linotte, a new autosomal gene in Drosophila involved with learning and memory. The linotte1 mutant was dervied from a PlacW transposon mutagenesis and was screened for three–hour memory deficits after classical conditioning of an olfactory avoidance response. Sensory and motor systems (olfactory acuity and shock reactivity) required for the classical conditioning experiments were normal in mutant linotte1 files-indicating that the mutation disrupts learning/memory specifically. A chromosomal deficiency of the 37D region, where the linotte1P insert was localized in situ, failed to complement linotte1's memory defect, and files from two lines homozygous for independent PlacW excisions show normal memory-indicating that the P insertion is responsible for the mutant phenotype. Additional behavior–genetic data suggest that linotte gene is non-vital.

Video recording system for the measurement of eyelid movements during classical conditioning of the eyeblink response in the rabbit

Classical conditioning of the eyeblink response in the rabbit is a popular model for studying the neural substrates of associative learning. Most of the common eyeblink recording techniques require invasive procedures. To perform experiments in intact animals, a non-invasive, high-speed video recording system was developed to measure eyeblink responses of rabbits during classical conditioning experiments. Besides being non-invasive, this method does not require excessive restraint of the animal. The PC-based system combines a Pulnix video camera with National Instruments video capture and timing hardware to control the experiment and acquire images of the peri-ocular region. The software developed for controlling these experiments also detects the eyeblink by measuring the movement of the upper and lower eyelids, the area of the exposed surface of the eye, and head movements in the sagittal plane. The time resolution of this relatively inexpensive system is 8.33 ms, and at a working distance of 0.8 m, it can detect movements as small as 0.11 mm.