Animal navigation studies have implicated structures in and around the hippocampal formation as crucial in performing path integration (a method of determining one's position by monitoring internally generated self-motion signals). Less is known about the role of these structures for human path integration. We tested path integration in patients who had undergone left or right medial temporal lobectomy as therapy for epilepsy. This procedure removed approximately 50% of the anterior portion of the hippocampus, as well as the amygdala and lateral temporal lobe. Participants attempted to walk without vision to a previously viewed target 2-6 m distant. Patients with right, but not left, hemisphere lesions exhibited both a decrease in the consistency of path integration and a systematic underregistration of linear displacement (and/or velocity) during walking. Moreover, the deficits were observable even when there were virtually no angular acceleration vestibular signals. The results suggest that structures in the medial temporal lobe participate in human path integration when individuals walk along linear paths and that this is so to a greater extent in right hemisphere structures than left. This information is relevant for future research investigating the neural substrates of navigation, not only in humans (e.g., functional neuroimaging and neuropsychological studies), but also in rodents and other animals.
Well-organized eating and grooming behaviors were elicited in cats by stimulation of a zone in the cerebellum that extended from the fastigial nucleus to the superior cerebellar peduncle. Behaviors appeared to result from the facilitation of specific sensorimotor mechanisms, rather than the induction of generalized "drive" states. The results emphasize the need for a broad view of cerebellar function.Several studies have investigated the effects of electrical stimulation of localized areas of the cerebellum in unanesthetized free-moving cats (1-6). The predominant effects reported have been relatively simple autonomic or tonic motor responses, such as pressor responses or postural changes. A few papers, however, have reported somewhat more complex responses such as licking, biting, or swallowing movements (5,6). Furthermore, in a previous study Berntson showed that coordinated sequences of grooming behavior can be elicited by stimulation of the superior cerebellar peduncle (7). In the present study, we examined the behavioral effects of electrical stimulation of the cerebellum in unanesthetized free-moving cats which were provided with a variety of goal objects, to determine whether grooming or other complex behaviors can be elicited from the cerebellum itself.The subjects were 15 cats, each surgically implanted with 16 chronic monopolar stimulation electrodes aimed for different regions of the cerebellum. Anatomical data from three additional cats of a previous study (7) are also included. After at least 5 days of postoperative recovery, food-and watersatiated cats were given two free-moving cerebellar stimulation tests separated by at least 24 hr. During each of these tests, all electrodes were tested at a wide range of voltage levels, with 50-Hz monopolar pulses of 100-,usec duration.The testing box (73 X 54 X 48 cm) contained dry cat chow, an anesthetized rat, and a foam-rubber block and a wood block each of about the same dimensions as a rat. After completion of testing, the brains were perfused with formalin, sectioned, and stained. Electrodes were localized by direct projection of the sections onto atlas diagrams of Snider and Niemer (8).Only those electrodes that produced consistent behaviors in both testing sessions are reported as effective. Details of the surgical, histological, and experimental procedures are essentially the same as those des*ibed in an earlier paper (7).Cerebellar stimulation evoked two main categories of complex species-characteristic behavior, eating and grooming (Table 1), in addition to more elementary motor responses which have been described in detail (1-6). Generally, elicited eating and grooming were vigorois;"reliable, and stimulation-2497 bound. Without stimulation, eating and grooming were virtually never seen under the conditions of the tests.Stimulation-induced eating resembled normal eating behavior. Upon stimulation, the cats approached the food, picked up pieces with their front teeth, shifted the food to the back of their mouths, and then chewed and swallowe...
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