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Neurosciences

Western University

Articles 361 - 368 of 368

Full-Text Articles in Social and Behavioral Sciences

Discrimination Of Computer-Graphic Stimuli By Mice: A Method For The Behavioral Characterization Of Transgenic And Gene-Knockout Models., T J Bussey, L M Saksida, L A Rothblat Aug 2001

Discrimination Of Computer-Graphic Stimuli By Mice: A Method For The Behavioral Characterization Of Transgenic And Gene-Knockout Models., T J Bussey, L M Saksida, L A Rothblat

Brain and Mind Institute Researchers' Publications

An automated method is described for the behavioral testing of mice in an apparatus that allows computer-graphic stimulus material to be presented. Mice responded to these stimuli by making a nose-poke toward a computer monitor that was equipped with a touchscreen attachment for detecting responses. It was found that C57BL/6 mice were able to solve single-pair visual discriminations as well as 3-pair concurrent visual discriminations. The finding that mice are capable of complex visual discriminations introduces the possibility of testing mice on nonspatial tasks that are similar to those used with rats, monkeys, and humans. Furthermore, the method seems particularly …

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Eye Position Sense Contributes To The Judgement Of Slant., F M James, S Whitehead, G K Humphrey, M S Banks, T Vilis Jan 2001

Eye Position Sense Contributes To The Judgement Of Slant., F M James, S Whitehead, G K Humphrey, M S Banks, T Vilis

Brain and Mind Institute Researchers' Publications

We measured monocular judgements of the slant of a cube face while varying eye position in the absence of stereoscopic and external lighting cues. Errors were found to be small, only 10% on average of the cube's eccentricity. Two factors appear to have contributed approximately equally to this error: an underestimate of cube slant as seen by the eye and an underestimate of eye position. When prism adaptation altered the sensed eye position, the pattern of slant judgements changed to reflect the altered sense of eye position.

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Eye Position Signal Modulates A Human Parietal Pointing Region During Memory-Guided Movements., J F Desouza, S P Dukelow, J S Gati, R S Menon, R A Andersen, T Vilis Aug 2000

Eye Position Signal Modulates A Human Parietal Pointing Region During Memory-Guided Movements., J F Desouza, S P Dukelow, J S Gati, R S Menon, R A Andersen, T Vilis

Brain and Mind Institute Researchers' Publications

Using functional magnetic resonance imaging, we examined the signal in parietal regions that were selectively activated during delayed pointing to flashed visual targets and determined whether this signal was dependent on the fixation position of the eyes. Delayed pointing activated a bilateral parietal area in the intraparietal sulcus (rIPS), rostral/anterior to areas activated by saccades. During right-hand pointing to centrally located targets, the left rIPS region showed a significant increase in activation when the eye position was rightward compared with leftward. As expected, activation in motor cortex showed no modulation when only eye position changed. During pointing to retinotopically identical …

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Local And Global Stereopsis In The Horse., B Timney, K Keil May 1999

Local And Global Stereopsis In The Horse., B Timney, K Keil

Brain and Mind Institute Researchers' Publications

Although horses have laterally-placed eyes, there is substantial binocular overlap, allowing for the possibility that these animals have stereopsis. In the first experiment of the present study we measured local stereopsis by obtaining monocular and binocular depth thresholds for renal depth stimuli. On all measures, the horses' binocular performance was superior to their monocular. When depth thresholds were obtained, binocular thresholds were several times superior to those obtained monocularly, suggesting that the animals could use stereoscopic information when it was available. The binocular thresholds averaged about 15 min arc. In the second experiment we obtained evidence for the presence of …

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Perceptual-Mnemonic Functions Of The Perirhinal Cortex., Murray, Bussey Apr 1999

Perceptual-Mnemonic Functions Of The Perirhinal Cortex., Murray, Bussey

Brain and Mind Institute Researchers' Publications

It is widely acknowledged that the perirhinal cortex, located in the ventromedial aspect of the temporal lobe, is essential for certain types of memory in macaque monkeys. For example, removal of the perirhinal cortex yields severe impairments on tests of stimulus recognition and stimulus-stimulus association. There is considerable disagreement, however, about the most accurate way to characterize the function of the perirhinal cortex; some views emphasize a role in perception whereas others posit a role exclusively in declarative memory. In this article, we review recent findings from anatomical, physiological and ablation studies in monkeys, and discuss related findings obtained in …

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Functionally Dissociating Aspects Of Event Memory: The Effects Of Combined Perirhinal And Postrhinal Cortex Lesions On Object And Place Memory In The Rat., T J Bussey, J L Muir, J P Aggleton Jan 1999

Functionally Dissociating Aspects Of Event Memory: The Effects Of Combined Perirhinal And Postrhinal Cortex Lesions On Object And Place Memory In The Rat., T J Bussey, J L Muir, J P Aggleton

Brain and Mind Institute Researchers' Publications

Reciprocal interactions between the hippocampus and the perirhinal and parahippocampal cortices form core components of a proposed temporal lobe memory system. For this reason, the involvement of the hippocampus in event memory is thought to depend on its connections with these cortical areas. Contrary to these predictions, we found that NMDA-induced lesions of the putative rat homologs of these cortical areas (perirhinal plus postrhinal cortices) did not impair performance on two allocentric spatial tasks highly sensitive to hippocampal dysfunction. Remarkably, for one of the tasks there was evidence of a facilitation of performance. The same cortical lesions did, however, disrupt …

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Fornix Lesions Can Facilitate Acquisition Of The Transverse Patterning Task: A Challenge For "Configural" Theories Of Hippocampal Function., T J Bussey, E Clea Warburton, J P Aggleton, J L Muir Feb 1998

Fornix Lesions Can Facilitate Acquisition Of The Transverse Patterning Task: A Challenge For "Configural" Theories Of Hippocampal Function., T J Bussey, E Clea Warburton, J P Aggleton, J L Muir

Brain and Mind Institute Researchers' Publications

Configural theories of hippocampal function predict that hippocampal dysfunction should impair acquisition of the transverse patterning task, which involves the concurrent solution of three discrimination problems: A+ versus B-; B+ versus C-; and C+ versus A-. The present study tested this prediction in rats using computer-graphic stimuli presented on a touchscreen. Experiment 1 assessed the effects of fornix lesions when the three problems were introduced sequentially (phase 1: A+ vs B-; phase 2: A+ vs B-, B+ vs C-; phase 3: A+ vs B-, B+ vs C-, C+ vs A-). Fornix lesions significantly facilitated acquisition of the complete transverse patterning …

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Triple Dissociation Of Anterior Cingulate, Posterior Cingulate, And Medial Frontal Cortices On Visual Discrimination Tasks Using A Touchscreen Testing Procedure For The Rat., T J Bussey, J L Muir, B J Everitt, T W Robbins Oct 1997

Triple Dissociation Of Anterior Cingulate, Posterior Cingulate, And Medial Frontal Cortices On Visual Discrimination Tasks Using A Touchscreen Testing Procedure For The Rat., T J Bussey, J L Muir, B J Everitt, T W Robbins

Brain and Mind Institute Researchers' Publications

Four experiments examined effects of quinolinic acid-induced lesions of the anterior cingulate, posterior cingulate, and medial frontal cortices on tests of visual discrimination learning, using a new "touchscreen" testing method for rats. Anterior cingulate cortex lesions impaired acquisition of an 8-pair concurrent discrimination task, whereas posterior cingulate cortex lesions facilitated learning but selectively impaired the late stages of acquisition of a visuospatial conditional discrimination. Medial frontal cortex lesions selectively impaired reversal learning when stimuli were difficult to discriminate; lesions of anterior and posterior cingulate cortex had no effect. These results suggest roles for the anterior cingulate, posterior cingulate, and medial …

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