Altered precision grasping in stumptail macaques after fasciculus cuneatus lesions.

Patterns of precision grasp are described in stumptail macaques (Macaca arctoides) before and after lesions of the fasciculus cuneatus (FC). Three monkeys were videotaped while reaching for and grasping small food items. From these videotapes, records were made of the style and outcome of each grasp. Kinematic measurements were also made to describe grip formation and terminal grasp. During grip formation, grip aperture was measured as the distance between the tips of the index finger and the thumb. For terminal grasp, the joint angles of the index finger were measured. The majority of grasps by normal monkeys were of the precision type, in which the item was carried between the tips of the index finger and thumb. Each normal monkey approached objects with a highly consistent grip formation; that is, the fingertips formed a small grip aperture during the approach, and the aperture varied little on repeated grasps. To grasp an item, the forefinger moved in a multiarticular pattern, in which the proximal joint flexed and the distal joint extended. As a result of this combination of movements, the forefinger pad was placed directly onto the object. Following FC transection, the monkeys were studied for 10 months, beginning 1 month after the lesion, to allow for recovery from the acute effects of surgery. The monkeys could grasp the food items, but they rarely opposed the fingertips in precision grasp. Grip formation was altered and was characterized either by excessive grip aperture or by little to no finger opening. All of the monkeys used the table surface to help grasp items. Combined multiarticular patterns of flexion and extension were never observed postoperatively; they were replaced by flexion at all joints of the fingers. These results suggest that the FCs are more important for precision grasping than for other, less refined grasp forms (e.g., power grasps; Napier, 1956). The FCs provide critical proprioceptive feedback to cerebral areas involved in the planning and/or the execution of these movements.     

Hyperphagia and hyperdipsia after locus coeruleus lesions in the stumptailed monkey.

Bilateral lesions of the nucleus locus coeruleus in 7 female stumptail monkeys were followed by long lasting hyperphagia and hyperdipsia. The percentage increase in weight at five weeks after lesioning correlated highly with 3-methoxy-4-hydroxy-phenethylene glycol (MHPG) concentration in the cerebral cortex. This relationship suggests that the effects are due to the locus coeruleus system and are not the result of variable destruction of the ventral noradrenergic or adjacent non-noradrenergic pathways.     

Analysis of tremulous movements after thalamotomy correlated to intrathalamic therapeutic lesions.

Residual tremulous movements after thalamotomy were examined using an accelerometer and EMG. Various types of tremor-provoking procedures were performed and the tremulous movements were classified according to the pattern of modificiation by these procedures. Four types of postoperative tremulous movements were noted, and a correlation was made to the intrathalamic therapeutic lesions.     

Amphetamine-induced locomotor activity and stereotypy after kainic acid lesions of the striatum.

Kainic acid injections were used to destroy cell bodies in the striatum without affecting afferent terminals of fibres of passage. Substantial decreases in choline acetyltransferase and glutamic acid decarboxylase were found particularly in the dorsal half of the striatum but no alteration in the marker enzyme for dopamine terminals, tyrosine hydroxylase. The locomotor activity inducing and stereotypical effects of the psychomotor stimulant drug, d-amphetamine, were tested in these animals and a marked and consistent $\text{increase}$ in the effects of amphetamine was found on both measures. This is interpreted in terms of a disruption of the striatonigral feedback system and as suggesting a possible dissociation of function within the striatum between the dorsal and the ventral parts.     

Persistence of sleep-temperature coupling after suprachiasmatic nuclei lesions in rats

The suprachiasmatic nucleus (SCN) regulates the circadian rhythms of body temperature (T(b)) and vigilance states in mammals. We studied rats in which circadian rhythmicity was abolished after SCN lesions (SCNx rats) to investigate the association between the ultradian rhythms of sleep-wake states and brain temperature (T(br)), which are exposed after lesions. Ultradian rhythms of T(br) (mean period: 3.6 h) and sleep were closely associated in SCNx rats. Within each ultradian cycle, nonrapid eye movement (NREM) sleep was initiated 5 +/- 1 min after T(br) peaks, after which temperature continued a slow decline (0.02 +/- 0.006 degrees C/min) until it reached a minimum. Sleep and slow wave activity (SWA), an index of sleep intensity, were associated with declining temperature. Cross-correlation analysis revealed that the rhythm of T(br) preceded that of SWA by 2-10 min. We also investigated the thermoregulatory and sleep-wake responses of SCNx rats and controls to mild ambient cooling (18 degrees C) and warming (30 degrees C) over 24-h periods. SCNx rats and controls responded similarly to changes in ambient temperature. Cooling decreased REM sleep and increased wake. Warming increased T(br), blunted the amplitude of ultradian T(br) rhythms, and increased the number of transitions into NREM sleep. SCNx rats and controls had similar percentages of NREM sleep, REM sleep, and wake, as well as the same average T(b) within each 24-h period. Our results suggest that, in rats, the SCN modulates the timing but not the amount of sleep or the homeostatic control of sleep-wake states or T(b) during deviations in ambient temperature.