June L. DeVito

Subcortical projections to the hippocampal formation in squirrel monkey (Saimiri sciureus)

Subcortical afferents to the hippocampal formation in squirrel monkey were investigated using horseradish peroxidase as a retrograde marker. Labeled cells were found in the medial septal area, the diagonal band of Broca, anterior and laterodorsal thalamic nuclei, reuniens and periventricular thalamic nuclei, lateral hypothalamus, supramamillary nucleus, and the dorsal and superior central midbrain raphe nuclei. These results in a primate confirm previous findings in rats and cats with the exception of the noradrenergic cell groups, where the interpretation of retrograde label was hampered by high levels of endogenous pigment.

Afferent projections to the hypothalamic area controlling emotional responses (HACER)

The Mesulam technique for horseradish peroxidase was used to study the subcortical afferent projections to a location in the hypothalamus that has been shown to control the complete cardiovascular (CV) response accompanying a specific emotional behavior. Major projections common to all baboons injected included the lateral septal nucleus; medial, cortical and basal amygdala; the anteroventral third ventricle area; the preoptic areas; the subiculum; the paraventricular nucleus of the thalamus; periventricular gray and the central gray of the midbrain; the midbrain tegmentum; locus ceruleus, parabrachial and raphe cells in the pons; and in the medulla, raphe nuclei, the nucleus of the solitary tract, in and around the dorsal motor nucleus of the vagus, and in the region of the nucleus ambiguus. Other projections in some but not all baboons included the subfornical organ and the midline and dorsomedial nuclei of the thalamus. The nucleus of the diagonal band of Broca was labeled to some degree with all injections but was most heavily labeled with the injection extending more laterally in the hypothalamus. These results fit well with physiological and behavioral studies dealing with neural control of emotional and CV responses and support the concept of an integrative area in the hypothalamus concerned specifically with the control of CV response accompanying emotion.

Unmyelinated axons in the pyramidal tract of the cat

Ultrastructural preparations revealed the presence of unmyelinated axons in the pyramidal tract (PT) of the adult cat. At the level of the medulla oblongata, unmyelinated axons constituted 8-15% of the total PT population. Axon diameters ranged from 0.05 to 0.06 micron with a mean of 0.18 micron. Although axons were distributed throughout the PT, their density was highest in the medial part.

An approach to quantifying various types of spontaneous activity.

The output of an activity-measuring device is fed into low- and high-gain cumulative recorder channels which are reset to zero after different time periods. The records, inscribed at various paper speeds, are easily quantified. The tracing patterns can be identified with specific activities of undisturbed animals. The activities are monitored by means of closed-circuit television.