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D A Benson

Publications and source records attributed to D A Benson.

25 records · Page 2Linked to original sources
PubMed1981

Single-unit activity in the auditory cortex of monkeys actively localizing sound sources: spatial tuning and behavioral dependency.

Single-unit recordings were made from the auditory cortex of unanesthetized rhesus monkeys which were trained to perform a second localization task. Recordings were made from 196 units in 4 animals. Five sound sources were located at 0 degrees (midline) and on either side at azimuths of 37.5 degrees and 75 degrees. Almost most units responded to each of the 5 sources, 49% of the units had peak firing rates for the source on the contralateral side at 75% azimuth. Another 26% of the units had peak firing rates at the 37.5 degrees contralateral location, while only 11% had peak rates for the ipsilateral locations. In order to determine whether the behavior of actively locating a sound source affected units in auditory cortex, response rates compared under two behavioral conditions: one which required the detection of a sound regardless of location and another condition which required identification of a sound's location. of the 196 units, 16 had different response rates for the two conditions, with 15 of the 16 units having higher evoked rates in the localization task. For the 16 units, the difference in firing rate was typically observed for a single speaker location. No correlation could be determined between a unit's location within the subdivisions of auditory cortex and its spatial tuning response properties or its dependency upon behavioral condition.

Animals↗
PubMed1978

Single-unit activity in the auditory cortex of monkeys selectively attending left vs. right ear stimuli.

Single-unit responses were recorded from the auditory cortex of rhesus monkeys that were performing an auditory selective attention task. Acoustic stimuli were presented randomly to either the left or right ear through headphones. In a given block of trials one ear was selected as the ear to be attended, and was indicated by lighting either a left or right response key. The animal's task was to press the lighted key whenever stimuli were presented to the attended ear, but to make no response to stimuli presented to the other ear. The attended ear was alternated on successive blocks of trials. Fourteen of 77 units showed significantly greater rates of evoked discharges for an attended stimulus than for an identical non-attended stimulus. The increase in stimulus-evoked activity was not accompanied by any increase in spontaneous activity or by any changes in the pattern of a unit's response. Changes in firing rate occurred at latencies as early as 20 msec.

Acoustic Stimulation↗
PubMed1976

Evoked unit activity in auditory cortex of monkeys performing a selective attention task.

Single-unit responses were recorded from the auditory cortex of rhesus monkeys performing a selective atteintion task which used combined light and sound stimuli. The animals were first trained to push a lever to the left for a noise burst and to the right for a tone burst, and then trained to push left for a left light and right for a right light. Subsequently, one of the four possible light and sound stimulus combinations (Noise + Left Light, Noise + Right Light, Tone + Left Light, Tone + Right Light) was randomly presented on each trial. In blocks of 100 trials only one part of the combined stimulus (either the light or the sound) determined the direction of lever push that would be reinforced. Responses of single units to identical sound stimuli were compared for blocks in which sound was the relevant cue and blocks in which light was the relevant cue. Typically, differences were in response strength without alteration of response pattern. Even the earliest response components (15-20 msec latency) could show changes. Two-thirds of the response comparisons showed differences in strength depending upon whether sound or light was the relevant cue, with about as many responses stronger for light relevant as for sound relevant. Independent of which modality was relevant, unit responses for trials in which both parts of the combined light and sound stimulus indicated the same direction of lever push were generally stronger than unit responses for trials in which the two parts of the combined stimulus signalled opposite directions of lever pushes.

Animals↗
PubMed1976

Anatomical study of cerebral asymmetry in the temporal lobe of humans, chimpanzees, and rhesus monkeys.

It is generally accepted that anatomical asymmetries in the temporal lobe language region of humans are associated with the asymmetrical representation of language function in the left hemisphere. Comparative measurements were taken of the length of the left and right Sylvian fissures of human, chimpanzee, and rhesus monkey brains. Measurements confirmed the findings of other studies that the human Sylvian fissure is longer on the left than on the right. The chimpanzee brains had a similar asymmetry but to a lesser degree than the human brains. The rhesus brains, however, showed no significant differences between left and right fissure lengths.

Animals↗
PubMed1976

Single unit study of binaural interaction in the auditory cortex of the chinchilla.

The primary aim of this investigation was to systematically compare for various stimulus conditions the relative influences of contralateral and ipsilateral acoustic stimulation on cortical single units in an unanesthetized preparation and to study the effects upon single unit responses of the dominant stimulus cues for sound localization--interaural intensity difference (deltaI) and interaural time difference (deltat). Recordings were obtained from 133 units in chinchillas immobilized by gallamine triethiodide. All units were found to be influenced by input from both ears. Unit thresholds for contralateral stimulation were lower and more discharges were elicited than for ipsilateral stimulation over a range of intensities from unit threshold intensity to 80 dB sound-pressure level. A predominance of contralateral influence was also observed when the number of stimulus-evoked discharges was plotted as a function of the deltaI or deltat. For 62% of the deltaI functions maximal responsiveness occurred for binaural stimuli that were more intense at the contralateral ear. Similarly, of the 36 units that showed sensitivity to deltat parameters for tone stimuli, 22 (61%) were maximally responsive at the contralateral-leading deltat intervals. For click stimuli, maximal responsiveness for all 21 deltat-sensitive units also occured for contralateral-leading stimuli. Certain observations in the study question the generality of the hypothesis that a particular cell invariantly encodes a specific deltat, i.e., that cells have 'characteristic delays'. First, most units tested at more than two frequencies showed maximal responsiveness at different deltat intervals depending upon stimulus frequency. Second, the deltat intervals for maximal responsiveness for half of the units tested were greater than the maximal interaural delays the animal could encounter naturally. Third, deltat functions from the same unit for click and tone stimuli showed poor correspondence. These findings suggest that the encoding of interaural time and intensity might depend on an inter-hemispheric comparison of the activity of neural populations as originally proposed by von Bekesy.

Acoustic Stimulation↗