Recent theoretical work has suggested that brain oscillations in the theta band are involved in active maintenance and recall of working memory representations. To test this theoretical framework we recorded neuromagnetic responses from 10 subjects performing the Sternberg task. Subjects were required to retain a list of 1, 3, 5 or 7 visually presented digits during a 3-s retention period. During the retention period we observed ongoing frontal theta activity in the 7-8.5-Hz band recorded by sensors over frontal brain areas. The activity in the theta band increased parametrically with the number of items retained in working memory. A time-frequency analysis revealed that the task-dependent theta was present during the retention period and during memory scanning. Following the memory task the theta activity was reduced. These results suggest that theta oscillations generated in frontal brain regions play an active role in memory maintenance.

Considerable progress has been made in developing models of cerebellar function in sensorimotor control, as well as in identifying key problems that are the focus of current investigation. In this consensus paper, we discuss the literature on the role of the cerebellar circuitry in motor control, bringing together a range of different viewpoints. The following topics are covered: oculomotor control, classical conditioning (evidence in animals and in humans), cerebellar control of motor speech, control of grip forces, control of voluntary limb movements, timing, sensorimotor synchronization, control of corticomotor excitability, control of movement-related sensory data acquisition, cerebro-cerebellar interaction in visuokinesthetic perception of hand movement, functional neuroimaging studies, and magnetoencephalographic mapping of cortico-cerebellar dynamics. While the field has yet to reach a consensus on the precise role played by the cerebellum in movement control, the literature has witnessed the emergence of broad proposals that address cerebellar function at multiple levels of analysis. This paper highlights the diversity of current opinion, providing a framework for debate and discussion on the role of this quintessential vertebrate structure.

A computer model is described for the de SQUID in which the two Josephson junctions are non-hysteretic resistively shunted tunnel junctions. In the absence of noise, current-voltage (I-V) characteristics are obtained as functions of the applied flux, ~ , SQUID inductance, L, junction critical a current, I , and shunt resistance, R. The effects of asymmetry in L' I ,. 0 0 4 5 6, 7 Zinnnerman and Silver, Schulz-DuBois, and by De Waele and DeBruyn Ouboter 8 9 for the symmetric SQUID, by Fulton, Clarke and Paterson, and Tsang and 10 11 Van Duzer for asymmetric SQUID, and by Fulton, Dunkleburger and Dynes, 12 and Tsang and Van Duzer for the SQUID with non-sinusoidal current-phase relationships. A qualitative discussion of the noise-free current-voltage characteristic for the SQUID in the small inductance limit has been given by DeWaele and DeBruyn Ouboter, 6 and by Tinkham. 3 However, no quantitative calculation of the flux dependence of the current-voltage characteristics has previously been made. * 10 An elegant alternative method of solution has been given by Tsang and Van Duzer.

Working memory (WM) is the ability to retain and associate information over brief time intervals. Functional imaging studies demonstrate that WM is mediated by a distributed network including frontal and posterior cortices, hippocampus, and cerebellum. In rodents, the presentation of stimuli in a WM task is followed by a reset of the phase of hippocampal theta. In this paper we report the observation of a similar phenomenon in normal human subjects. Neuromagnetic responses were recorded during presentation of a set of digits and a subsequent probe of the retained items. All stimuli were presented with a fixed temporal pattern. We observed phase reset of Ϸ7 Hz theta in left hippocampus Ϸ120 ms after probe stimuli, whereas reset of theta in right hippocampus was visible Ϸ80 ms prior to these anticipated stimuli. The duration of stimulus-locked theta increased with memory load, with a limiting value of Ϸ600 ms for 5-7 retained items. We suggest that, as in rats, stimulus-locked theta may index involvement of human hippocampal networks in the cognitive processing of sensory input. The anticipatory phase reset of theta indicates involvement of hippocampus in right hemisphere and cerebellar timing networks. Hippocampal structures are essential for orientation to perturbations in the sensory scene, a function that requires use of a context established by a constellation of stimuli. We suggest that the initiation and maintenance of stimulus-locked hippocampal theta observed here may facilitate processing of potentially salient and͞or novel input with respect to a context established by the contents of WM.