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PubMed1980

Test for effects of visual and position cues on T-maze learning in toads.

This research was concerned with the effects of different classes of cues on the ability of toads (Bufo marinus) to learn an escape task, discrimination learning, in a T-maze. The cues were either a black or white brightness cue, a right or left position cue, or combinations of brightness and position cues. The toads were given a .6-A shock until they made the correct response. Results suggested that toads are capable of learning a discrimination task based on either a position or brightness cue. However, the rate of learning was influenced by strong aversion to the white arm when escaping from an aversive stimulus. No particular preference for either brightness or position cues was found independent of this aversion.

Animals↗
PubMed2002

Associative learning and elemental representation: II. Generalization and discrimination.

This paper follows on from an earlier companion paper (McLaren & Mackintosh, 2000), in which we further developed the elemental associative theory put forward in McLaren, Kaye, and Mackintosh (1989). Here, we begin by explicating the idea that stimuli can be represented as patterns of activation distributed across a set of units and that different stimuli activate partially overlapping sets (the degree of overlap being proportional to the similarity of the stimuli). A consequence of this view is that the overall level of activity of some of the units representing a stimulus may be dependent on the nature of the other stimuli present at the same time. This allows an elemental analysis in which provision for the representation of configurations of stimuli is made. A selective review of studies of generalization and discrimination learning, including peak shift, transfer along a continuum, configural discrimination, and summation, suggests that the principles embodied in this class of theory deserve careful consideration and will form part of any successful model of associative learning in humans or animals. There are some phenomena that require an elemental/associative explanation.

Association Learning↗
PubMed1991

Basolateral amygdaloid multi-unit neuronal correlates of discriminative avoidance learning in rabbits.

Basolateral (BL) amygdaloid multi-unit activity was recorded as male albino rabbits learned to avoid a foot-shock unconditioned stimulus (US) by stepping in an activity wheel to an acoustic (pure tone) warning stimulus (CS+). A second tone (CS-) of different auditory frequency than the CS+ was presented in an irregular order on half of the conditioning trials but was never followed by the US. BL amygdaloid neurons developed, in the first session of conditioning, enhanced CS-elicited discharges relative to discharges recorded during pretraining with tones and noncontingent US presentations (excitatory plasticity), and greater discharges to the CS+ than to the CS- (discriminative plasticity). The discriminative plasticity attained maximal magnitude as the rabbits reached the asymptote of behavioral discrimination, and persisted during post-asymptotic training. Peak excitatory plasticity occurred in the session of the first significant behavioral discrimination and declined during the asymptotic and post-asymptotic stages of training. Similar patterns of excitatory and discriminative plasticity in structures directly interconnected with the BL nucleus (anterior cingulate cortex; medial dorsal thalamic nucleus) and effects of lesions suggest that the neurons in these areas participate in a circuit involved in mediation of avoidance learning.

Amygdala↗
PubMed1993

On the role of the hippocampus in learning and memory in the rat.

An overview of lesion experiments concerned with the involvement of the hippocampus in learning and memory in the rat is presented. Multiple injections of small amounts of ibotenic acid were used to selectively remove the hippocampus (dentate gyrus, hilar cells, CA1-CA3 pyramidal cells). Similar selective, axon-sparing ibotenate lesions of hippocampus were used in a series of learning and memory experiments employing tasks that are thought to be important in hippocampal function. The performance of rats with the hippocampus removed was compared with that of control animals in the acquisition and retention of spatial versus nonspatial information, forgetting of spatial and nonspatial information, contextual learning, recognition memory and concurrent discrimination learning, and complex representational learning (conditional discrimination and negative patterning learning). The general finding that rats without a hippocampus were impaired on those tasks that required the utilization of spatial and contextual information stands in contrast with the spared performance that was found in learning about and handling (even complex) nonspatial information. Rather than support for views that emphasize a role for the hippocampus in specific memory processes (working memory, declarative memory, temporary memory buffer, configural learning), the present results are more compatible with the idea that the hippocampus plays an especially important role in processing and remembering spatial and contextual information. The limited data that are available using more selective lesions of related hippocampal formation structures (entorhinal cortex, subiculum) suggest that these structures also make important contributions to learning and memory, and that some of these contributions may be different from those made by the hippocampus.

Animals↗
PubMed2001

Behavioural correlates of striatal glial fibrillary acidic protein in the 3-nitropropionic acid rat model: disturbed walking pattern and spatial orientation.

The 3-nitropropionic acid animal model is a model where excitotoxicity, mitochondrial dysfunction and oxidative stress, mechanisms common to various neurodegenerative diseases, are involved. The present study investigated whether behavioural alterations in this model were related to striatal damage. Wistar and Lewis rats were exposed to 3-nitropropionic acid and their behavioural performance (open field, walking pattern and Morris Water Maze task) was tested after the injections and after a recovery period of 3 weeks. No changes in activity were found in the open field test. Altered walking pattern was observed in the footprint analysis, although a different response was observed in the Wistar rats compared to the Lewis rats. Initially increased latency times were observed during visual discrimination learning in the Morris Water Maze task in 3-nitropropionic acid-treated Wistar rats compared to Wistar controls. During spatial discrimination learning (invisible platform) in the Morris Water Maze task the swimming velocity was decreased in both rat strains as a result of 3-nitropropionic acid treatment. Increased striatal glial fibrillary acidic protein concentration in Wistar rats correlated with several parameters of the footprint analysis and with the latency and distance in visual as well as spatial discrimination learning in the Morris Water Maze. It is concluded that measurement of walking pattern and spatial orientation performance are sensitive indicators to monitor behavioural changes in relation to striatal degeneration in the 3-nitropropionic acid animal model. In addition, Lewis rats are less sensitive towards 3-nitropropionic acid treatment than Wistar rats.

Animals↗
PubMed1978

Extent of recovery from neonatal damage to the cortical visual system in cats.

Cats that received either marginal or marginal plus extramarginal lesions as 3-day-old kittens were assessed on a series of tests of visually guided behavior. These cats were not conspicuously different from normal controls in avoiding obstacles or in activity level. Yet these same operated cats were severely impaired in performance on the visual cliff and in visual discrimination learning, even when the lesions were limited to the geniculocortical portion of the visual system. However, maximum losses in pattern and form discrimination learning were observed only in cats with severe retrograde degeneration in both the lateral geniculate nucleus and the complex of the pulvinar and nucleus lateralis posterior. Photically evoked potentials were recorded in the lateral regions of the neocortex more reliably from operated cats that had made fewer errors in discrimination learning than from more severely debilitated cases; this relation was present even among cases with nearly equivalent amounts of retrograde degeneration in the visual thalamus. These findings suggest that in the cat (a) recovery of vision is incomplete after neonatal lesions of the visual cortex and (b) a cortical system lateral to the geniculocortical projections may be involved in pattern vision.

Animals↗
PubMed2004

Learning to discriminate between ligand-bound and disulfide-bound cysteines.

We present a machine learning method to discriminate between cysteines involved in ligand binding and cysteines forming disulfide bridges. Our method uses a window of multiple alignment profiles to represent each instance and support vector machines with a polynomial kernel as the learning algorithm. We also report results obtained with two new kernel functions based on similarity matrices. Experimental results indicate that binding type can be predicted at significantly higher accuracy than using PROSITE patterns.

Algorithms↗
PubMedDate not supplied

Collaborative Behavioral Teratology Study: programmed data entry and automated test systems.

The automated laboratory systems described in this paper were developed for use at the National Center for Toxicological Research (NCTR) and each of five collaborating laboratories. These laboratories participated in a study designed to evaluate the intra- and interlaboratory reliability and sensitivity of several behavioral test methods used in developmental toxicity studies. This paper describes two microcomputer systems. System I was designed to control stimulus delivery to and record behavioral responses from rats during a visual discrimination learning task and to accept data from physical landmark, negative geotaxis, and olfactory discrimination evaluations. The microprocessor system was an S-100 bus, Z-80 processor with 8K PROM, 16K RAM, nine 8-bit parallel I/O ports, and one serial I/O port. For discrimination learning, the animal testing apparatus consisted of six operant chambers, equipped with two stimulus lights, two nose-poke apertures each containing a phototransmitter and receiver, an electromechanical liquid dispenser unit, and a reward bowl also containing a photodiode. Each chamber was interfaced with the microprocessor at a parallel I/O port which permitted the delivery of response- or time-contingent control signals for the lights and liquid dispenser units. System II controlled stimulus delivery and recorded behavioral responses from rats during an auditory startle habituation task, and also recorded rodent activity levels in figure 8 mazes for periods of 1, 4, or 23 hours. The microprocessor system was an S-100 bus, Z-80 processor with 8K PROM, 16K RAM, nine parallel I/O ports, an analog to digital (A/D) I/O board, and one serial I/O port.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed2002

Mismatch negativity shows that 3-6-year-old children can learn to discriminate non-native speech sounds within two months.

Using 3-6-year-old children as subjects, we describe the neural plasticity accompanying the concurrent learning of a foreign language in a natural environment. Children were monitored for 6 months as they either enrolled in schools or daycare centers where only Finnish was spoken (Control group) or as they joined a French school or a daycare center where French was spoken 50-90% of the time (Experimental group). Whereas mismatch negativity (MMN)--a brain's electrical change-detection response--for a French speech contrast was initially absent or very small in both groups, it was conspicuous 2 months after Finnish children had joined a French kindergarten. Consequently, the data suggest that youngsters can learn to distinguish non-native speech sounds in natural language environment without any special training in just a couple of months. Accordingly, these data herald the vast potential MMN may entail for studying language learning, especially in situations where behavioral responses cannot be readily elicited.

Analysis of Variance↗
PubMed1991

Historical context of state dependent learning and discriminative drug effects.

Drug-induced state dependent learning (SDL), as well as similar effects on memory retrieval exercised by physiological states, have been known since 1830. Before 1950, understanding of this area derived primarily from clinical descriptions of somnambulism, dream recall, fugue states, and cases of multiple personality. After 1950, experimental demonstrations of the properties of SDL and drug discriminations (DDs), along with a series of changes in the DD procedure, have led to the DD paradigm that is currently employed, and which has properties that make it an extremely useful tool for preclinical investigation of a variety of pharmacological and psychological questions. These conceptual and technical developments have resulted in widespread acceptance of the DD paradigm as a preclinical research method. This paper reviews the nineteeth and twentieth century history of clinical observations, concepts, and experiments, that have led to our current status of knowledge about drug discriminations and SDL.

Journal Article↗
PubMedDate not supplied

Dissociation between the effects of damage to perirhinal cortex and area TE.

Perirhinal cortex and area TE are immediately adjacent to each other in the temporal lobe and reciprocally interconnected. These areas are thought to lie at the interface between visual perception and visual memory, but it has been unclear what their separate contributions might be. In three experiments, monkeys with bilateral lesions of the perirhinal cortex exhibited a different pattern of impairment than monkeys with bilateral lesions of area TE. In experiment 1, lesions of the perirhinal cortex produced a multimodal deficit in recognition memory (delayed nonmatching to sample), whereas lesions of area TE impaired performance only in the visual modality. In experiment 2, on a test of visual recognition memory (the visual paired comparison task) lesions of the perirhinal cortex impaired performance at long delays but spared performance at a very short delay. In contrast, lesions of area TE impaired performance even at the short delay. In experiment 3, lesions of the perirhinal cortex and lesions of area TE produced an opposite pattern of impairment on two visual discrimination tasks, simple object discrimination learning (impaired only by perirhinal lesions), and concurrent discrimination learning (impaired only by TE lesions). Taken together, the findings suggest that the perirhinal cortex, like other medial temporal lobe structures, is important for the formation of memory, whereas area TE is important for visual perceptual processing.

Animals↗
PubMed1991

[The role of GABA-ergic transmission of caudate-putamen nucleus (CPN) in the control of conditioned behavior in rats].

Using the method of bilateral injection of GABA (100 micrograms/microliters) and muscimol (0.1 micrograms/microliters) into the caudate-putamen nucleus (CPN) we have studied the role of GABA-ergic transmission of CPN in the control of conditioned behavior. In order to compare the effects of GABA and muscimol on two behavioral paradigms, rats of either sex weighing 160-180 g were trained to perform discrimination learning and conditioned avoidance response. A tone (1 kHz, 80 dB) was used as a conditioned stimulus. After bilateral injections of GABA and muscimol into the trained rats' CPN respectively, the conditioned avoidance response was inhibited temporarily, whereas the discrimination learning remained almost unchanged. In addition, the inhibitory effect of muscimol on the conditioned avoidance response was attenuated or even abolished by following bilateral intra-CPN injection of picrotoxin (0.1 micrograms/microliters for each side). As a control, the same volume of saline was injected into CPN bilaterally, and it showed that there was no change of both the conditioned avoidance response and the discrimination learning. The results show that the GABA-ergic transmission of CPN does play a role in the control of avoidance conditioning in rats, and thus support the suggestion that GABA-ergic transmission of the caudate-globus pallidus plays an important role in the control of conditioned behavior.

Animals↗
PubMed2003

Intradimensional and extradimensional shifts in spatial learning.

Animals trained on 2 discriminations learn the 2nd rapidly if the relevant stimuli are from the same dimension as the 1st (an intradimensional or ID shift) but slowly if the relevant stimuli for the 2 problems are from different dimensions (an extradimensional or ED shift). Four experiments examined ID and ED shifts in spatial learning. Rats trained on 2 spatial problems learned the 2nd more rapidly than rats whose 1st problem had been nonspatial. But this difference between ID and ED shifts depended on the spatial relationship between rewarded (S+) and unrewarded (S-) alternatives in the 2 spatial problems. The results imply that rats trained on a spatial discrimination do not learn to attend to all spatial landmarks but only to those that serve to differentiate S+ and S-.

Animals↗