Effects of septal and caudate lesions were compared on brightness and spatial discrimination and reversal. Further analyses of the effects of these lesions and low-level electrostimulation of the septal area were made on a spatial-alternation problem. Septal lesions selectively impaired reversal of spatial, but not brightness, discrimination. Conversely, caudate lesions selectively disrupted brightness discrimination. Septal lesions, in contrast to septal stimulation or caudate lesions, blocked acquisition of spatial alternation and generally induced faster performance time. These results provide evidence of at least two dissociable dysfunctions associated with septal lesions. Further dissociation of septal and caudate functions is indicated, but the data do not rule out some commonality of operation.

2-way avoidance behavior and concurrent intertrial activity were studied in the shuttle box in relation to stimulus and shock conditions; data were obtained on spontaneous activity and reactivity to CS. Facilitatory effects of septal lesions on avoidance behavior were independent of shock level, CS, ambient levels of stimulation, and gross manifestations of hyperreactivity. The facilitation was associated with higher intertrial activity, reflecting low incidence of freezing responses, but was not secondary to the heightened activity. Discriminative avoidance conditions did not alter the lesion-induced facilitation. Septal lesions also enhanced reactivity to phptic stimuli. The multiplicity of effects cautions against any unitary explanation of the septal syndrome.

No abstract

Rats were trained preoperatively in a bar-pressing situation to discriminate between 2 tones, based upon intermittent food reinforcement in the presence of one of them. Septal lesions produced sustained increases in bar pressing during nonreinforced conditions and also retarded extinction of bar pressing. Cingulate lesions facilitated extinction. A follow-up study of septal effects further demonstrated increased perseverative errors during acquisition of a simultaneous brightness discrimination, but no serious impairment in total acquisition scores or retention. The results are consistent with the view that the septal area exercises inhibitory control over somatomotor activity.Experimental lesions in the septal area of the brain transform normally docile laboratory rats into wild, often vicious animals that react in exaggerated fashion to stimulation (Brady & Nauta, 1953;King, 1958). These effects, which typically subside within about 2 weeks, focused attention initially upon the role of the septal area in emotional processes that are expressed in shock-motivated behavior. The lesions were thought to increase "emotional reactivity" or "irritability."More recently, other investigators have challenged this view (Kaada, Rasmussen, & Kveim, 1962; McCleary, 1961). In line with electrophysiological evidence which implicates the septal-subcallosal area in the inhibition of somatic as well as autonomic responsivity (Kaada, 1960), they emphasize the more general role of these structures in the inhibition of behavioral responses and attribute the major effects of the lesions to an impairment in response inhibition. Supporting evidence is based almost exclusively upon the contrasting pattern of changes found in passive and active shock-avoidance behavior.

No abstract