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

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represents to a lesser extent a similar ‘activation’. When the anterior group
did not approach, they showed a high frequency of behavioural change to test
stimuli that were most similar in structure to the train-trill. In response to sti-
muli that have message content, the posterior group did not approach, but
showed a high frequency of behavioural change.

High tension is reasonably seen as an alert posture that reflects a degree of
arousal. It is compatible with a high frequency of behavioural change but not
with approach. High tension was seen after the approach response for a short
period in the anterior group and for a longer period in the posterior group
when consummation did not follow. (In the training programme search is
followed by low tension after consummation.) It is suggested that search and
approach, frequency of behavioural change and high tension represent a pro-
gression from activation to arousal; (this parallels the so-called ‘reasoning’
process that has partly been attributed to limbic interactions by Pribram and
McGuinness, 1975).

Overt behaviour

Results. The incidence of the four behavioural components (M, S, LT, HT)
after the test stimuli showed a complex pattern of changes, but they broadly
confirm that there were two similar groups (T_b3j5 and T_4j7j8 ) and one mixed
group (T_2j6,9) of test stimuli. For reasons of clarity of presentation, the data
from each similar group are presented as means (Fig. 6 and 7). All differences
are significant at a level of 5% or less.

(1) Filter-trills. (Fig. 6)

Two features are common to both lesion groups. The first emerges from a
comparison of the train-trill (first extinction trial) and T₁. On the first extinc-
tion trial both lesion groups showed more search than they and controls did
after Ti. Search continued longer for the posterior group. Secondly in res-
ponse to the filter-trills the lesion groups showed less search than preopera-
tive levels, but more than sham-controls. After the most filtered trill (T₅)
they showed more high tension than preoperatively. The anterior group show-
ed some differences. Correlating with a high frequency of behavioural com-
ponent changes the anterior group showed more movement after the stimulus
than preoperatively or sham-control levels. In response to T₃ these phases
gave way to more low tension than in the posterior group.

(2) Novel stimuli. (Fig. 7)

By comparison with the filter-trills neither lesion group showed such large
increases of search behaviour. But like their response to filter-trills they show-
ed more search and less high tension than sham-controls. Nonetheless both
groups showed less low tension than sham controls which might indicate a
degree of novel stimulus-induced arousal, (shortly after the stimulus). There
were also differences between the lesion groups. As with the training stimulus
regime the anterior group showed more low tension, less high tension after
a shorter search phase than the posterior group.

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