Unilateral lesions of the caudate nucleus selectively blocked lever pressing with the forepaw contralateral to the lesion; response with the ipsilateral forepaw was not altered. These findings were verified with 2nd-stage lesions of the opposite caudate, although 1-stage bilateral lesions produced more variable effects. Control ablation of sensorimotor cortex typically did not interfere with contralateral response and the integrity of sensorimotor cortex was not necessary for blocking of response induced by caudate lesions. With other operant conditions and FI reinforcing contingencies, bilateral caudate lesions disrupted preoperatively formed response-suppression during early segments of each FI. These data implicate the caudate in sensorimotor functions and some form of inhibitory regulation of behavior.

Rats trained in a bar-pressing situation to discriminate between either 2 tones or tone and no-tone, based upon intermittent food reinforcement in the presence of S*, displayed consistent and often severe impairment on retention performance after large bilateral lesions in the amygdaloid area. Histological analysis also implicated the putamen in these effects. Amygdaloid impairment was closely associated with increased responding under nonreinforced conditions, with no concomitant increases in responding to S" 1 ". Hippocampal lesions, by contrast, increased responding to S* without seriously affecting responding to S~. Amygdaloid impairment on stimulus generalization occurred after 2tone but not after tone-no-tone training, and seemed to reflect a defect in generalization of S~ or in behavioral contrast as part of a basic disturbance in S" control of behavior.

In an effort to localize and interrelate amygdaloid functions in the rat required for (a) suppression of response during nonreinforced components of a discrimination and in extinction of response, and (b) those required for development of a conditioned emotional response (CER), lesions were prepared in different parts of the amygdaloid complex and overlying putamen. Large lesions of the amygdala blocked formation of the CER and interfered with response suppression under nonreinforced conditions but not to the extent of seriously disrupting discrimination performance. Putamen lesions, on the other hand, seriously disrupted discrimination performance but had no reliable effect upon CER. Results on subtotal amygdaloid lesions implicated the medial region in the area of basomedial and cortical and perhaps central nuclei in both the control of nonreinforced behavior and formation of the CER. The more lateral components of the amygdala appear less essential for these functions.

No abstract

Two experiments were conducted to determine the effect of acute heat stress on late-stage chicken embryos. Embryos were incubated at a normal control temperature (37.5 degrees C.) for 16 days and were then subjected to 40.6, 43.3, 46.1 or 48.9 degrees C. for various periods of time in another incubator of the same type. At the end of the stress period all embryos were placed back into the control incubator for the remainder of the incubation period. Exposure of embryos for 24 hours to a temperature of 40.6 degrees C, caused no major detrimental effects on hatchability. Exposure for 6 hours to the temperature of 43.3 degrees C, caused a decrease in hatchability with a severe decline in hatchability occurring after 9 hours of exposure. Exposure to 46.1 degrees C. for 3 hours or 48.9 degrees C for 1 hour killed all embryos. Chicks which hatched following a severe heat stress had a high incidence of clubbed, wiry down and exhibited an unsteady gait.