Peter Orlebar Bishop. 14 June 1917—3 June 2012

Peter Orlebar Bishop was an Australian neurophysiologist renowned for his ingenious quantitative approach to the study of the mammalian visual system and his great ability to attract a large number of talented people to visual research. Peter’s research was based on specially designed, precise instrumentation and data quantification applied mainly to analysis of the response properties of single neurones in the principal dorsal thalamic visual relay nucleus, the dorsal lateral geniculate nucleus (LGNd) and the primary visual cortex. This quantitative bent was evident throughout Peter’s entire research career: starting with the design and construction of innovative DC amplifiers; to his quantitative analysis of optics, ‘schematic eye’ for the cat, which rivalled Gullstrand’s schematic eye for humans; to creating and demonstrating validity of the concept of ‘projection lines’ in the representation of contralateral visual field in different cellular layers of the LGNd of mammals with frontally positioned eyes and discovery of massive binocular input to single LGNd neurones. Peter’s engineering approach was probably at its heuristic peak when it revealed many details of binocular interactions at the level of single neurones in the primary visual cortex—the interactions which appear to underpin overall mechanisms underlying stereopsis, the high precision binocular depth sense.

Peter Orlebar Bishop 1917–2012

Peter Orlebar Bishop was an Australian neurophysiologist renowned for his ingenious quantitative approach to study of the mammalian visual system and great ability to attract a large number of talented people to visual research. Peter's research was based on specially designed, precise instrumentation and data quantification applied mainly to analysis of the response properties of single neurones in the principal dorsal thalamic visual relay nucleus, the dorsal lateral geniculate nucleus (LGNd) and the primary visual cortex. This quantitative bent was evident throughout Bishop's entire research career:starting with the design and construction of innovative DC amplifiers; through to his quantitative analysis of optics—‘schematic eye' for the cat, which rivaled Gullstrand's schematic eye for humans; to creating and demonstrating validity of the concept of ‘projection lines' in the representation of contralateral visual field in different cellular layers of the LGNd of mammals with frontally positioned eyes and discovery of a very substantial binocular input to single LGNd neurones. The engineering approach of Peter was probably at its heuristic peak when it revealed many details of binocular interactions at the level of single neurones in the primary visual cortex—the interactions that appear to underpin overall mechanisms underlying stereopsis, the high precision binocular depth sense.

A gadolinium and pH-sensitive hyperpolarization-activated cation current in acutely isolated single neurones from Fasciola hepatica

Fasciola hepatica, a parasitic flatworm belonging to the Class Trematoda, is one of the first metazoan groups to possess a centralized nervous system. However, the electrophysiological properties of neurones in F. hepatica are largely unknown. In the present study, we acutely isolated viable neurones from F. hepatica and characterized their electrophysiological properties. A hyperpolarization-activated cation current was recorded in the cells using the whole-cell patch-clamp. The current was found to be activated slowly at membrane potentials negative to 0 mV and did not display any time-dependent inactivation. This current was reduced by 1 mM Gd3+ to the level of the leak current, while 3 mM of Cs+ had no effect. However, the current was inhibited by extracellular acidosis in the pH range 7.0–7.8, and the membrane potentials of these cells were depolarized by extracellular alkalosis in the pH range of 5.8 to 8.2. Gd3+ (1 mM), which inhibited the pH-sensitive hyperpolarization-activated cation current, also hyperpolarized the cells. In summary, we isolated single neurones from F. hepatica, and these were found to express a pH-sensitive hyperpolarization-activated cation current. This current may participate in the membrane depolarization of F. hepatica neurones during alkaline challenge.

Gaze field properties of eye position neurones in areas MST and 7a of the macaque monkey

The activity of parietal cortex neurones primarily related to eye position (EP neurones) was studied in macaque monkeys with the aim of precisely defining the neurones' gaze fields (GF) and comparing them in two functionally different areas, MSTd and 7a. Discharge rates of single neurones in the inferior parietal lobule and in the underlying cortex of the superior temporal sulcus were recorded in two Java monkeys while the animals fixated a steady visual target positioned at several different points on a video screen. The GFs were then drawn as a regression surface fitting the mean discharge rates. Cells tonically influenced by the angle of gaze were found in both areas. The GFs most often took the form of a nearly planar surface best characterized as a ramp tilted towards a hemifield or quadrant of the visual field, shifted eccentrically with respect to the straight ahead (primary position), and with a midpoint centred between 0 deg and 20 deg of gaze eccentricity and saturation between 10 deg and 35 deg. In a minority of cases, the discharge rate was nearly maximal at the primary position and decreased to a minimum within 35 deg of eccentricity. In other instances, the GFs were peaked surfaces, limited to a restricted part of visual space. EP neurones, while showing similar gaze fields in areas MST and 7a, were found intermingled with functionally different types of cells. The results suggest that EP neurones similar to those already described in several areas of the monkey parietal cortex are present also in area MST. These cells, by signalling the degree of gaze eccentricity from the primary position, encode gaze position in an orbito-centered frame extending up to 30–35 deg from the straight-ahead. The role of EP neurones might be to supply contiguous elements with a gaze eccentricity signal required for visuo-motor processes such as the control of tracking movements.