EFFECTS OF HIPPOCAMPAL, AMYGDALA, HYPOTHALAMIC AND PARIETAL LESIONS ON A CLASSICALLY CONDITIONED FEAR RESPONSE

Experiments investigating the effects of limbic system lesions in a modified classical conditioning situation were performed on 68 rats. Pre- and post-operative tests were given to parietal and amygdalectomized Ss. Postoperative tests were given to parietal, hippocampal, and amygdalectomized Ss. Hypothalamic and amygdaloid Ss showed no evidence of learning the test response. Contrary to previous reports, it was found that animals with small hippocampal lesions were able to learn the test response. The observed learning deficits were discussed in terms of possible receptor mechanisms for painful stimuli controlled by basolateral amygdaloid nucleus and ventromedial hypothalamus.

NEUROLOGICAL FACTORS IN READING DISABILITY

An overview is presented of that portion of the literature on reading disability wherein neurological defect is seen as causal or correlative. From the publication of Hinshelwood's "Congenital Word Blindness" (1917) to the present, investigators have considered the possible association of reading difficulty with genetically determined neurological defect, with cerebral damage, with biochemical imbalance inhibiting synaptic transmission, and with some form of maturational lag.

THE EFFECTS OF CEREBRAL LESIONS ON INTELLECTUAL FUNCTION: A REVIEW OF CURRENT RESEARCH TRENDS

The literature of the psychological effects of brain injury is extensive and disconnected. It abounds in inadequate definitions, incompatible theories and disagreements as to appropriate methods of investigation. This situation results partly from the variety of disciplines which guide different investigators; but it results too from the great logical difficulties encountered by anybody who seeks to throw light on normal intelligent behaviour by studying the effects of cerebral lesions. Some have even argued that such attempts are always unprofitable (47, 77).