Role of the medial and lateral caudate-putamen in mediating an auditory conditional response association

Rats with quinolinic acid lesions of the medial or lateral caudate-putamen (CPu) and controls were tested for performance of a previously learned auditory conditional response association task. The task involved the selection of two possible responses when presented with one of two different tones. Results indicated that lesions of either the medial or the lateral CPu produced a sustained deficit in the auditory conditional response association task. Only the lateral CPu lesioned rats exhibited transient motor problems immediately following surgery, but these problems did not interfere with the execution of the appropriate responses. It is suggested that both the medial and the lateral CPu are involved in response selection and response separation within egocentric space.     

Spatial co-location and infants'' learning of auditory-visual associations

The role of spatial co-location between sight and sound in infants' cross-modal learning was examined in three experiments. Four-and 6-month-old infants were familiarized with a toy and an accompanying soundtrack. Across conditions, spatial congruity between sight and sound was varied. Following familiarization, infants were tested to determine under which conditions they learned to associate the toy with the sound. Results indicated age-related differences in how discrepant in location a sight and sound could be for infants to form a cross-modal association based on the amodal invariant of co-location. Specifically, 4-month-olds formed cross-modal associations under conditions of less precise co-location than did 6-month-olds. Parallel improvements in infants' sound localization abilities across this age span are likely a contributing factor to the observed developmental trend in cross-modal learning.     

Cortical evoked potentials as indicators of auditory-visual cross-modal association in young adults

Auditory evoked potentials (AEPs) were studied from scalp locations Cz and Oz on 37 adults aged 20–22 years during sensori-sensorial association of a weak sound (S) and a strong flash of light (L). After sound alone repetition (habituation), S-L association modified AEP: first, it caused a generalized orienting response expressed as increasing of Cz and Oz amplitude AEPs. Then, this pattern gave way to an activation limited to the Oz lead: the increase of amplitude was then concomitant with shortened latencies when compared to sound-alone-habituated responses. Inter-individual differences were observed since these occipital modifications were recorded only on 26 subjects. The other 11 subjects did not exhibit any occipital modifications following S-L association. For them, the main modification was a strong decrease of Cz AEP induced by S-L association. These two groups also differed in their capacity to ignore irrelevent stimuli which is higher in the first group (AEP amplitude habituation with sound-alone repetition) than in the second one (no AEP habituation).     

Role of the primary somatosensory cortex in motor learning: An rTMS study

Somatosensation is thought to play an important role in skilled motor learning. The present study investigated how healthy adults learn a continuous implicit motor task when somatosensation is altered by 1 Hz repetitive transcranial magnetic stimulation (rTMS) delivered over the primary somatosensory cortex (S1). Twenty-seven right-handed participants enrolled in a two-part experiment. In Experiment 1, we verified that 20 min of 1 Hz rTMS over S1 disrupted cutaneous somatosensation (indexed by two-point discrimination) in the wrist/hand; the impact of 1 Hz rTMS on wrist proprioception (tested by limb-position matching) was variable. Sham rTMS had no effect on either measure. We exploited these effects in Experiment 2 by pairing either 1 Hz or sham rTMS with practice of a continuous tracking task over two separate sessions on different days. Implicit motor learning was indexed on a third, separate retention test day when no rTMS was delivered. Across practice in Experiment 2, both the 1 Hz and sham rTMS groups showed improved tracking performance; however, 1 Hz rTMS was associated with less accurate tracking and smaller improvements in performance. Importantly, at the no rTMS retention test the effects of altering sensation with stimulation over S1 were still evident in the persistently less accurate tracking behavior of the 1 Hz rTMS group. The current study shows that disruption of somatosensation during task practice impairs the magnitude of change associated with motor learning, perhaps through the development of an inaccurate internal model.     

Crossmodal learning in newborn infants: Inferences about properties of auditory-visual events

The majority of research on infant crossmodal perception has addressed the question of whether infants 4 months and older demonstrate the ability. By contrast, the focus in the present study was on newborns and the primary goal was twofold: to determine if newborns can learn arbitrary sight-sound pairings and to evaluate possible inferences that neonates make when repeatedly presented arbitrary sight-sound pairings. Alert neonates were familiarized with toy-sound pairs using an infant-controlled habituation procedure. They were then given a violation-of-expectancy test to determine if they had learned these sight-sound pairings and drawn any inferences about certain properties of these bimodal events. Results supported the conclusion that infants just a few hours old can learn sight-sound pairings. Furthermore, the findings suggested that newborns expected sight-sound pairs to remain colocated even when they move to a new location, they recognized that the sound was an attribute of a specific object, and they recognized that a specific spatial location was not an attribute of the sight-sound pair. Thus, infants made important and correct inferences based on limited experiences with specific auditory-visual events, and they did so just after birth. Implications of these findings for theories of crossmodal perceptual development are discussed.     

Role of responsibility in conditional reasoning

A series of recent studies showed that facilitation on the Wason Selection Task could be produced by perceived utilities. The present work was aimed at testing whether a similar factor could also be involved in human reasoning performance in the context of responsibility. We supposed that the motivation of the subject assuming responsibility is affected by normative goals. These goals prescribe the actions and the results to be achieved, also considering the different social roles. In this experiment the responses of different groups of subjects (N = 270) to a selection task were compared in two different conditions involving different responsibility contexts. The results show that the subjects' strategies in searching for possible violators depended on the condition (responsibility vs no responsibility). In particular, only in the context of responsibility were the performances elicited by conditional rules characterised by a falsification strategy.     

Successive and conditional discrimination learning in pigs

We studied the ability of pigs to discriminate tone cues using successive and conditional discrimination tasks. Pigs (n = 8) were trained in a successive discrimination Go/No-Go task (Experiment 1) to associate a Go-cue with a reward at the end of a runway and a No-Go-cue with the absence of reward. Latency to reach the goal-box was recorded for each cue-type. Learning of a conditional discrimination task was compared between low-birthweight (LBW, n = 5) and normal-birthweight (NBW, n = 6) pigs (Experiment 2) and between conventional farm (n = 7) and Göttingen miniature (n = 8) pigs (Experiment 3). In this active-choice task, one cue signalled a response in a right goal-box was correct and a second cue signalled a response in a left goal-box was correct. Cues were differentially rewarded. The number of sessions to learn the discrimination and number of correct choices per cue-type were recorded. In Experiment 1, four out of eight pigs showed learning on the task, that is, a higher latency to respond to the No-Go-cue, within 25 sessions. In Experiment 2, eight out of 11 pigs learned the discrimination within 46 sessions. LBW learners learned faster than NBW learners. In Experiment 3, all 15 pigs learned the task within 16 sessions. Göttingen miniature pigs learned faster than conventional farm pigs. While some methodological issues may improve the Go/No-Go design, it is suggested that an active-choice task yields clearer and more consistent results than one relying on latency alone.     

Perceptual capacity of the isolated visual cortex in the cat

The split-brain approach was utilized in 6 cats to test the degree of functional autonomy in the visual system. The central visual cortex of one hemisphere was isolated by the removal of most of the extravisual neocortex of the same hemisphere. Visual inflow was restricted to the isolated side in four cases by sectioning the crossed optic fibres at the chiasma and masking one eye and in two cases by section of the contralateral optic tract. The isolation produced severe deficits in visual performance, although all cases retained some ability to learn and to recall simple pattern discriminations. The results of two- and three-stage removals of the non-visual cortex, and of terminal section of the callosum, as well as histology of the lateral geniculate nucleus indicated that geniculo-striate damage was not the limiting factor. Removal of fronto-parietal cortex produced as much or more decrement in visual discrimination than did removal of temporal cortex.     

Associative change in the representations acquired during conditional discriminations: further analysis of the nature of conditional learning

Three experiments with rats investigated how the associative strengths of the representations that underlie conditional learning change when they are conditioned in compound. The results of each experiment suggest that the representation whose associative strength is most discrepant from the asymptote supported by the outcome of the trial undergoes the greatest change in associative strength. These results parallel those from simple Pavlovian conditioning (e.g., R. A. Rescorla, 2000). are inconsistent with unique-cue and configural accounts of conditional learning, and support a connectionist analysis of learning in which a "winner-takes-all" rule applies to the hidden units that can be activated and acquire associative strength at a given point in time.     

Errorless learning of a conditional temporal discrimination

In the present study we extended errorless learning to a conditional temporal discrimination. Pigeons' responses to a left-red key after a 2-s sample and to a right-green key after a 10-s sample were reinforced. There were two groups: One learned the discrimination through trial and error and the other through an errorless learning procedure. Then, both groups were presented with three types of tests. First, they were exposed to intermediate durations between 2 s and 10 s, and given a choice between both keys (stimulus generalization test). Second, a delay from 1 s to 16 s was included between the offset of the sample and the onset of the choice keys (delay test). Finally, pigeons learned a new discrimination in which the stimuli were switched (reversal test). Results showed that pigeons from the Errorless group made significantly fewer errors than those in the Trial-and-Error group. Both groups performed similarly during the stimulus generalization test and the reversal test, but results of the delay test suggested that, on long stimulus trials, responding in the errorless training group was less disrupted by delays.     

Learning conditional frequencies in a probability learning task

The study was prompted by a theoretical discussion of probability learning by Estes (1976). In three separate experiments, subjects were presented with frequency information in the form of wins and losses among 3 teams, and later predicted future wins and losses. Frequencies were devised so that conditional win frequencies for a pair of teams were either inconsistent or consistent with marginal win frequencies for each team. In experiment 1, when subjects predicted future events on the basis of known past frequencies, predictions were generally based on conditional frequencies. In experiment 2 six blocks of observations were presented, with predictions following each block. What little learning did occur was in the direction of the conditional frequencies. Subjects in experiment 3 were able to learn conditional frequencies when given explicit instructions to do so. Results were discussed in terms of a two-stage hypothesis generation model that might operate within the framework of an associative theory of probability learning.     

Observational learning of a conditional hue discrimination in pigeons

Three experiments examined a relationship between cooperation and observational learning in pigeons using procedures similar to Skinner (1962). In Experiment 1, dyads cooperated by searching and pecking nearly simultaneously on the correct pair of adjacent keys of a 2 × 2 matrix. The dyads learned to search for the correct keys in a coordinated fashion, but only if they were permitted to watch one another's performance. Experiment 2 disconfirmed the hypothesis that the coordinated performance of cooperating pigeons reflects an unlearned response tendency to peck at locations close to where the other bird is pecking. Experiment 3 demonstrated that prior cooperation training involving an observer and demonstrator pigeon facilitated subsequent observational learning of a conditional hue discrimination. Cooperation training appeared to facilitate observational learning by establishing the demonstrator's peck response as an instructional stimulus which indicated the reward significance of the discriminative stimuli.     

A role for stimulus generalization in conditional discrimination learning

In each of three experiments on discrimination learning by rats, whether or not a 10-sec target stimulus was followed by food was determined by the nature of a 2-min background stimulus that accompanied it. A conditional discrimination was employed in Experiment 1 such that background A indicated food would follow one target but not the other, whereas this relationship between the targets and food was reversed in the presence of background B. Experiment 2 employed two feature-positive discriminations. Subsequent test trials revealed that the background for one discrimination was able to enhance responding during the target for the other discrimination. Experiment 3 employed a feature-positive and a feature-negative discrimination prior to test trials in which each target was presented separately during a compound of both background stimuli. The compound enhanced responding to the target from the feature-positive discrimination and reduced it to the target from the feature-negative discrimination. We suggest that to accommodate all these findings, the best explanation is provided by a configural model of Pavlovian conditioning.