Klaus Peter Hoffmann

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In the intermediate and deep layers of the superior colliculus (SC), a well-established oculomotor structure, a substantial population of cells is involved in the control of arm movements. To examine the reference frame of these neurons, we recorded in two rhesus monkeys (Macaca mulatta) the discharges of 331 neurons in the SC and the underlying(More)
When reaching for an object we usually look at it before we touch it with the hand. This often unconscious eye movement prior to the arm movement allows guiding of the final part of the hand trajectory by visual feedback. We examined the temporal and spatial coordination of this control system by psychophysical measurements of eye and arm movements of naive(More)
THE DORSAL lateral geniculate nucleus (LGNd) of the cat is a principal relay nucleus on the direct pathway from the retina to the visual cortex, and several parameters of its organization as a relay are well established. First, relay cells of the LGNd have either onor off-center receptive fields (16), because each relay cell receives direct excitatory drive(More)
Reaching with the arm to a newly appearing target is usually preceded by a saccadic eye movement. Neurons in the superior colliculus (SC) constitute one important brain structure controlling saccades. Yet, the SC also contains reach neurons activated during arm movements, whose location extends also deeper into the underlying mesencephalic reticular(More)
We studied the discharge of neurons from both the superior colliculus (SC) and the underlying mesencephalic reticular formation (MRF) and its relation to the simultaneously recorded activity of 11 arm muscles. The 242 neurons tested with a center-out reach task yielded 2,586 pairs of neuron/muscle cross-correlations (normalized, such that perfect(More)
The mode of visual information processing during visuospatial tasks differs across species and is supposed to depend on evolutionary and ecological factors. Humans show reaction times that increase with angular disparity when tested in mental rotation tasks. Pigeons show a time-independent rotational invariance that possibly evolved in response to the(More)
cATs REARED under various conditions of visual deprivation are deficient in their subsequent performance of certain visual tasks (6, 19). Wiesel and Hubel (15-17, 25-28) have sought the physiological basis of these effects by comparing receptivefield properties of single visual neurons of normhlly reared cats to those of visually deprived cats. Their(More)
Velocity selectivity of 92 LGN cells was measured quantitatively using long, narrow light or dark bars of high contrast in N2O-anesthetized and paralyzed cats. The optimal velocities of the main responses to a moving light bar, representing center responses (i.e., due to entering the ON center or leaving the OFF center) were significantly lower for X-cells(More)
Cells in the pretectal nucleus of the optic tract (NOT) of rats, cats and monkeys were retrogradely labeled with horseradish peroxidase (HRP) stereotaxically injected into the inferior olive (IO). A procedure for stabilizing the tetramethylbenzidine (TMB)-HRP reaction product was used to visualize combined TMB-HRP and immunohistochemically localized(More)