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Apperceptive visual agnosia is normally held to be a specific deficit in 'apperception' - a hypothetical postsensory stage in visual processing. This paper describes the investigation of a patient diagnosed as suffering from a classical apperceptive agnosia resulting from carbon monoxide poisoning. Controlled behavioural testing confirmed the apparent(More)
Monkeys were trained to press whichever of two panels showed a small, circular, luminous stimulus. Their brightness thresholds were measured by decreasing the luminance of this stimulus, titrating their performance to the 75 y0 correct level, and averaging over 1000 trials. Both frontal eye-field and superior collicular lesions produced a small but(More)
Superior collicular, frontal eye-field and posterior parietal lesions increased the time taken to find a circular target among other geometrical shapes. The collicular monkeys were considerably more impaired than the other groups, suggesting that the superior colliculus is the main neural structure underlying this highly practised visual search task.(More)
Rhesus monkeys were tested on a visual search task in which they had to find and retrieve a peanut from a display of visually similar but inedible objects. The speed with which they did so was measured. Animals in which the superior colliculi or frontal eye-fields had been removed took longer to find the peanut than two operated control groups. Animals with(More)
  • R Latto
  • 1986
Macaque monkeys with bilateral lesions of either the frontal eye-fields (Area 8) or the inferior parietal lobule (Area 7a or PG) were compared with unoperated controls on their ability to perform a series of 8 pre-operatively learnt visual discriminations. Simple non-spatial discriminations were not affected, but the frontal group was affected when the(More)
Ten cynomolgus monkeys were trained to follow a fixed route through a whole-body maze consisting of 3 X 3 matrix of 9 compartments, all with interconnecting doors. Two monkeys learned to use proprioceptive guidance such that they tended to produce the same sequence of movements even if they entered the maze by a different door. They were not impaired by(More)
The effects of inferior parietal cortex lesions (Area 7a/PG) and bilateral transection of the fornix were compared within a single species (cynomolgus monkeys) and using a single paradigm of route running in a traditional (fixed entry and exit) whole-body maze. Experiment 1 showed that Area 7a/PG but not fornix lesions impaired post-operative retention of(More)