Attentive, Affective, and Adaptive Behavior in the Cat: Sensory deprivation of the forebrain by lesions in the brain stem results in striking behavioral abnormalities.

Abstract

Lesions of the lateral portion of the upper midbrain, involving medial, lateral, spinal, and trigeminal lemnisci primarily, result in a consistent syndrome of symptoms in the cat. (i) There is a marked sensory deficit, characterized mainly by sensory inattention and poor localization in the tactile, proprioceptive, auditory, gustatory, and nociceptive modalities, where direct pathways are interrupted. Similar defects appear in vision and olfaction where no known direct or primary paths are interrupted. (ii) These cats are characterized by a lack of affect, showing little or no defensive and aggressive reaction to noxious and aversive situations and no response to pleasurable stimulation or solicitation of affection or petting. The animals are mute, lack facial expression, and show minimal autonomic responses. (iii) They show a hyperexploratory activity characterized by incessant, stereotyped wandering, sniffing, and visual searching, as though hallucinating. This behavior appears to be centrally directed and is very difficult to interrupt with environmental stimuli. (iv) They also demonstrate exaggerated oral activities: they snap in response to tactile stimulation of the lips, seizing and swallowing small objects even if inedible; they overeat; they hold objects too large to swallow (a mouse, a catnip ball) firmly clamped in the mouth for long periods of time; they mount and seize other animals (rat, cat, dog, monkey) by the back or the neck; they lick and chew the hair and skin of the back or tail incessantly when confined in a cage. In interpreting these results we emphasize the view that the syndrome is due chiefly to the extensive, specific, sensory deprivation produced by interruption of the lemnisci at the rostral midbrain. The relation of these findings to the effects of sensory isolation in man and animals, to the effects of midbrain lesions and neodecortication, to parietal lobe syndrome in primates, and to the behavior of autistic children is discussed. It is our belief, from these studies, that the symptoms produced by interruption of the lemnisci, characterized by a high degree of somatotopic and modality localization, are due to a loss of patterned sensory input to the forebrain, particularly to the neocortex and to the rostral midbrain. Without a patterned afferent input to the forebrain via the lemnisci, the remaining portions of the central nervous system, which include a virtually intact reticular formation, seem incapable of elaborating a large part of the animal's repertoire of adaptive behavior.