The present research examines the effect of spatial (object-centered) attentional constraints on pattern recognition. Four normal subjects and two right-hemisphere-damaged patients with left visual neglect participated in the study. Small, letterlike, prelearned patterns served as stimuli. Short exposure time prevented overt scanpaths during stimulus presentation. Attention was attracted to a central (midsagittal) hation point by precuing this location prior to each stimulus presentation. Minute (up to 1.5° of visual angle) rightward and leftward stimulus shifts caused attention to be allocated each time to a different location on the object space, while remaining in a fixed central position in viewercentered coordinates. The task was to decide which of several prelearned patterns was presented in each trial. In the normal subjects, best performance was achieved when the luminance centroid (LC; derived from the analysis of low-spatial frequencies in the object space) of each pattern coincided with the spatial position of the precue. In contrast, the patients with neglect showed optimal recognition performance when precuing attracted attention to locations within the object space, to the left of the LC. The normal performance suggests that the LC may serve as a center of gravity for attention allocation during pattern recognition. This point seems to be the target location where focal attention is normally directed, following a primary global analysis based on the low spatial frequencies. Thus, the LC of a simple pattern may serve as the origin point for an object-centered-coordiate-frame (OCCF), dividing it into right and left. This, in turn, serves to create a prototype description of the pattern, in its own coordinates, in memory, to be addressed during subsequent recognition tasks. The best match of the percept with the stored description may explain the observed advantage of allocating attention to the LC. The performance of the brain- damaged patients can be explained in terms of neglect operating in the OCCE.

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Responsiveness of auditory cortex (AC) units of awake squirrel monkeys to a natural sequence of species-specific calls was not significantly different from their responsiveness to a reverse playback of the sequence. No dependency was noted between the percentage of responding units and the average intensity of sounds, their spectral content or their order of presentation. The effectiveness of the sounds in eliciting responses was variable even when the sequence was produced in an unchanging behavioral context. Comparison of these findings with earlier results of individual vocalizations presented normally or backward in an isolated manner suggest that responsiveness of AC neurons to continuous sounds is lower than their responsiveness to isolated sounds, whether natural or artificial.

"Cognitive" auditory event-related potentials (ERPs) were mapped to examine the putative conscious responsiveness of eight patients in a postcoma unawareness (PCU) state and of eight matched normal controls. A "passive P3" paradigm was used to evaluate waves N2, P3, and Slow Waves of the ERPs. Results showed that the signal/noise ratio of the patients' waveshapes was poorer than that of the controls. Yet, on the whole, no between-group significant differences were noted for most of the averaged characteristics of the waves. In general, in the patients, the left hemisphere was dominated by negative potentials relative to the right one, whereas in the controls, the opposite asymmetry was apparent. Thirty-eight percent of the patients had passive N2 and P3 waves, and 67% of the responders regained consciousness (versus none of the non-responders). These findings suggest that the presence of intact "cognitive" waves is compatible with a higher probability for improvement, although nondetection of certain waves at the postcoma unawareness state does not necessarily indicate the worst prognosis.