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Results for “Discrimination Learning”

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PubMed2005

Cross-modal plasticity revealed by electrotactile stimulation of the tongue in the congenitally blind.

In sensory substitution, information acquired with one sensory modality is used to accomplish a task which is normally subserved primarily by another sensory modality. We used PET to study cross-modal plasticity in the congenitally blind, using electrotactile stimulation of the tongue. Blind (n = 6) and sighted blindfolded controls (n = 5) were scanned before and after they were trained to use their tongue in a Snellen orientation detection task. Results showed that both groups of subjects learned the discrimination orientation task after seven 1 h training sessions. Before training, no significant changes in regional cerebral blood flow (rCBF) were observed in the occipital cortex in either group. In sharp contrast, activity in the occipital cortex increased after practice for the blind, but not for the sighted, providing evidence for training-induced plasticity in the blind. An inter-regional correlation analysis showed that task-related rCBF changes in left posterior parietal cortex were positively correlated with rCBF changes in the occipital area of the trained blind. These data reveal that cross-modal plasticity in the blind develops rapidly and that the occipital cortex is part of a functional neural network for tactile discrimination in conjunction with the posterior parietal cortex. Our data further show that the tongue can act as a portal to convey somatosensory information to visual cortex.

Adult↗
PubMed1963

Brain functions.

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Appetite↗
PubMed2006

Haptic object localization in the vibrissal system: behavior and performance.

Using their large mystacial vibrissas, rats perform a variety of tasks, including localization and identification of objects. We report on the discriminatory thresholds and behavior of rats trained in a horizontal object localization task. Using an adaptive training procedure, rats learned to discriminate offsets in horizontal (anteroposterior) location with all, one row, or one arc of whiskers intact, but not when only a single whisker (C2) was intact on each cheek. However, rats initially trained with multiple whiskers typically improved when retested later with a single whisker intact. Individual rats reached localization thresholds as low as 0.24 mm (approximately 1 degree). Among the tested groups, localization acuity was finest (<1.5 mm) with rats that were initially trained with all whiskers and then trimmed to one arc of whiskers intact. Horizontal acuity was finer than the typical inter-vibrissal spacing (approximately 4.8 mm at contact points). Performance correlated with the net whisking spectral power in the range of 5-25 Hz but not in nonwhisking range of 30-50 Hz. Lesioning the facial motor nerves reduced performance to chance level. We conclude that horizontal object localization in the rat vibrissal system can reach hyperacuity level and is an active sensing process: whisker movements are both required and beneficiary, in a graded manner, for making accurate positional judgments.

Animals↗
PubMed2004

Entorhinal cortex lesions disrupt the relational organization of memory in monkeys.

Recent accounts suggest that the hippocampal system critically supports two central characteristics of episodic memory: the ability to establish and maintain representations for the salient relationships between experienced events (relational representation) and the capacity to flexibly manipulate memory (flexible memory expression). To test this proposal in monkeys, intact controls and subjects with bilateral aspiration lesions of the entorhinal cortex were trained postoperatively on two standard memory tasks, delayed nonmatchingto-sample (DNMS) and two-choice object discrimination (OD) learning, and three procedures intended to emphasize relational representation and flexible memory expression: a paired associate (PA) task, a transitive inference (TI) test of learning and memory for hierarchical stimulus relationships, and a spatial delayed recognition span (SDRS) procedure. The latter assessments each included critical "probe" tests that asked monkeys to evaluate the relationships among previously learned stimuli presented in novel combinations. Subjects with entorhinal cortex lesions scored as accurately as controls on all phases of DNMS and OD, procedures that can be solved on the basis of memory for individual stimuli. In contrast, experimental monkeys displayed deficits relative to controls on all phases of the PA, TI, and SDRS tasks that emphasized the flexible manipulation of memory for the relationships between familiar items. Together, the findings support the conclusion that the primate hippocampal system critically enables the relational organization of declarative memory.

Animals↗
PubMed1962

The effect of two schedules of primary and conditioned reinforcement.

Of 23 pigeons, 11 received continuous reinforcement for key pecking, and 12 received an FR 10 schedule of reinforcement. The birds were then tested without food, but with potential conditioned reinforcers presented either on the same schedule as in training, on the other schedule, or not at all. Each bird in the subgroup trained on CRF and tested with S(r)'s at FR 10 not only gave more responses in testing than did each bird in both subgroups receiving no S(r)'s, but also gave more responses than did each bird in the S(r) subgroup receiving CRF training and S(r)'s at CRF. Cumulative records are presented to show the effects of different schedules of conditioned reinforcers.

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