Title:
|
Differentiation of function of the right and left cerebral hemispheres in man
|
Experiments which have investigated differences of function of
the right and left cerebral hemispheres by studying ear asymmetry are
reviewed, and literature relating to the two click threshold, the task
used in this series of experiments, is summarised. Two reaction time
studies establish a perceptual factor in the ear asymmetry effect and
subsequent experiments explore the nature of this perceptual asymmetry_
A signal detection method is developed which, unlike the psychophysical
threshold method, reveals greater sensitivity in detection of
two clicks presented to the left ear than to the right ear when clicks
are presented with a contralateral burst of white noise, or with
preceding shock, but little difference between ears without white noise
or shock. Caffeine citrate also increases the right/left ear difference.
The effects of temporal intervals between white noise onset or
shock and click presentation, and of laterality of white noise or
shock are investigated. Interaction effects are again obtained, and
periodicity effects are noted which suggest the role of attention
mechanisms in the ear asymmetry effect.
It is suggested that two major factors are involved in the task:
detection of two clicks and pitch discrimination. The former is
considered to be an index of cortical arousal. The possibility of
hemispheric differences in arousal is discussed and a method for
investigating individual differences in arousal is suggested. Thelatter is considered to reveal differentiation of function of the
cerebral hemispheres in an auditory discrbnination task mainly
involving pitch discrimination. The phenomenon is interpreted as
being primarily perceptual, but attention mechanisms are also
probably involved.
Although the results obtained are reliable, the interpretation
is tentative and much further investigation is suggested
|