DISCRIMINATORY APPROACH TO AUDITORY STIMULI IN GUINEA FOWL (NUMIDA MELEAGRIS) AFTER HYPERSTRIATAL∕HIPPOCAMP- AL BRAIN DAMAGE

237

Fig. 4. For three groups of Guinea fowl this diagram shows the frequency of occurrence
of feeding and movement (vertical axis) in successive 5-s periods (horizontal axis) for 1
min following a food-trill. The left-hand diagrams show preoperative and the right-hand
diagrams show postoperative data. The symbols to the left of each diagram show the mean
probability (with SD) for each behaviour taken from the 30 s preceding the trill stimulus.
Each data point represents the mean for 20 trials. (Because of the possibility of several
foot movements in a 5-s period, the vertical axis for M represents the mean of foot move-
ments. )

Control group: preoperative ∙---∙, postoperative ∙- - -∙; anterior group: preoperative

o——o, postoperative o- - -o; posterior group: preoperative x---x, postoperative x- - -x.

trials that distinguished the groups in the late stimulus period. This negative
finding is important as it suggests that there is no gross impairment in the
holding or removal of information from memory.

There was a high degree of search behaviour shown by both lesion groups
initially. Further on the first trial, when reward was expected, both lesion
groups showed an increased incidence of change between behavioural compo-
nents with respect to prestimulus levels (+7.8). This measure could be an in-
dicator of an internal state, for this level of change was only otherwise attain-
ed after the ‘arousal’-trill (T₆, below).

Test stimuli

Duration of approach

Results. Inspection of the duration of approach by controls (Table II) shows

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