BRAIN RESEARCH LABORATORY

W. (Liam) Burke

Research in this laboratory in 1993 was in two separate areas: (i) central visual pathways, research carried out in association with Chun Wang and Bogdan Dreher in the Department of Anatomy & Histology, and (ii) the myoclonic effects of gallamine and curare, research conducted in collaboration with Iqbal Ramzan of the Department of Pharmacy.

RESEARCH in 1993

Monocular inhibitory interactions between the X and Y channels in the dorsal lateral geniculate nucleus (LGNd) of the cat

The selective pressure-blocking technique was used to eliminate conduction in the Y optic nerve fibres and the centre-surround antagonism in the receptive fields of LGNd cells was used to show that Y fibres contribute to this antagonism in X LGNd cells. Recent papers have suggested that there is no interaction between the X and Y systems at the LGNd level. In contrast results from the above research showed a considerable cross-talk.

Sensitivity of neurones in area 21a and posteromedial lateral suprasylvian (PMLS) area in the visual cortex of the cat to the motion of two-dimensional textured background ('visual noise')

Only a small proportion (25%) of neurones in area 21a can be excited (and then only weakly) by the movement of visual noise per se. By contrast, it was found that nearly half of the neurones in PMLS area can be excited by this stimulus and this excitation is strong. These results were consistent with the notion that area 21a is mainly involved in visual pattern analysis while the PMLS area is mainly concerned with visual motion analysis, including that of self-induced motion. There is, however, some interaction between the 'form' and 'motion' channels in area 21a. In particular, the magnitude of responses of area 21a neurones to elongated contours was significantly reduced during the simultaneous movement of the textured visual background. Furthermore, relative motion between the noise background and the contour stimuli had a modulatory effect on the direction selectivity of area 21a neurones.

Myoclonus due to gallamine and curare

These neuromuscular blocking agents do not normally cross the blood-brain barrier to any significant degree. However, in a decerebrate cat they gradually pass into the brain. If a neuromuscular blocking concentration of gallamine is maintained in the cardiovascular system, after about 3 days the concentration in the cerebrospinal fluid (CSF) becomes equal to that in the plasma. In the brain these substances were found to induce widespread synchronized contractions of all muscles which became very rhythmical at about 8-10 Hz. The substances were equally effective if injected into the CSF of a normal (i.e., not decerebrated) cat. The contractions of the muscles were found to be synchronized with slow waves in the inferior olive (see figure), but it remained to be demonstrated that the contractions were initiated in the inferior olive. The myoclonic effects of gallamine persisted for a day or more after the concentration in the CSF had dropped to a very low level. At the same time an unidentified substance appeared in the CSF.

RESEARCH PLANNED for 1994

The following will be investigated: myoclonic effects of gallamine and curare; elucidation of the nature of the unidentified substance referred to above; demyelination and remyelination in pressure-blocked optic nerves; properties of axonal conduction in demyelinated optic nerve fibres; role of Y input to area PMLS; role of Y system in the plasticity of visual cortical neurones.

D-Tubocurarine and gallamine elicit slow waves in the inferior olive and rhythmical discharges in motor nerves. A, 2 mg D-tubocurarine was injected into the cisterna magna of a pentobarbitone-anaesthetized cat 9 hours before the records were taken. B, 4 mg gallamine triethiodide was injected intracisternally about 5 hours after decerebration under a short-lasting anaesthetic; the recordings were made 30 minutes later. Time calibration applies to all records.

COLLABORATIONS

The Y system and central visual pathways in the cat: Dr B. Dreher, Dept of Anatomy & Histology (1988-present).

Relation of Y system to transmitter receptors in visual system: Dr V. Balcar, Dept of Anatomy & Histology (1991-present).

Gallamine and myoclonus: Dr I. Ramzan, Dept of Pharmacy (1988-present). Demyelination and remyelination in cat optic nerve: Dr B. Harrison, Dept of Biological Sciences, Univ. of Technology, Sydney (1989-present) and Dr K. Turlejski, Nencki Institute, Warsaw (1992-present).

Conduction properties of demyelinated optic nerve fibres: Prof. W.R. Levick, Neuroscience Division, John Curtin School of Medical Research, A.N.U. (1990-present).

FUNDING in 1993 and 1994

ARC	Interaction between components 		Burke W		1991

of the visual input to the cat Dreher B 1992

cerebral cortex 1993 $43,400

(Administered by Physiology;

Physiology share = 50%)

NHMRC The Y system and the visual Dreher B 1992

cortex of the cat Burke W 1993 $40,040

(Administered by Anatomy & Histology: 1994 $41,314

Physiology share = 50%)

NHMRC Autoradiography of high affinity Balcar V 1993 $42,410

uptake of L-glutamate in the CNS Dreher B 1994 $42,410?

(Administered by Anatomy & Histology: Burke W

Physiology share = 0%)

Total for 1993: $41,720

Total for 1994: $20,657

5-YEAR RESEARCH PUBLICATIONS

JOURNAL ARTICLES

1989

FitzGibbon T, Burke W (1989) Representation of the temporal raphe within the optic tract of the cat. Visual Neuroscience, 2, 255-267

1991

Cottee LJ, FitzGibbon T, Westland K, Burke W (1991) Long survival of retinal ganglion cells in the cat after selective crush of the optic nerve. European Journal of Neuroscience, 3, 1245-1254

1992

Burke W, Dreher B, Michalski A, Cleland BG, Rowe MH (1992) The effects of selective pressure block of Y-type optic nerve fibers on the receptive field properties of neurons in the striate cortex of the cat. Visual Neuroscience, 9, 47-64

Dreher B, Michalski A, Cleland BG, Burke W (1992) The effects of selective pressure block of Y- type optic nerve fibers on the receptive field properties of neurons in area 18 of the visual cortex of the cat. Visual Neuroscience, 9, 65-78

Burke W, Ramzan I (1992) Myoclonus in the decerebrate cat produced by gallamine. Brain Research, 580, 189-196

Levine MW, Cleland BG, Zimmerman RP (1992) Variability of responses of cat retinal ganglion cells. Visual Neuroscience, 8, 277-279

Chan L-P, Freeman AW, Cleland BG (1992) The rod-cone shift and its effect on ganglion cells in the cat's retina. Vision Research, 32, 2209-2219

1993

Dreher B, Michalski A, Ho HT, Lee CWF, Burke W (1993) Processing of form and motion in area 21a of cat visual cortex. Visual Neuroscience, 10, 93-115

Early 1994

Wang C, Dreher B, Burke W (1994) Non-dominant suppression in the dorsal lateral geniculate nucleus of the cat: laminar differences and class specificity. Experimental Brain Research, 97, 451-465

CHAPTERS IN BOOKS

Burke W (1989) A review of methods of selective inactivation of X and Y visual systems as a means of studying their function. Seeing Contour and Colour, Kulikowski JJ, Dickinson CM, Murray IJ eds, Pergamon Press, Oxford, 207-215

Burke W (1994) central actions of curare and gallamine: implications for reticular reflex myoclonus? Neurobiology and Disease: Contributions from Neuroscience to Clinical Neurology, Bostock H, Kirkwood PA, Pullen AH, eds, Cambridge University Press, Cambridge, in press.

CONFERENCE ABSTRACTS AND PRESENTATIONS in 1993

Burke W, Dreher B, Wang C (1993) Binocular non-dominant suppression of dorsal lateral geniculate nucleus cells in the cat depends on the level of activity in the cells. Proceedings of the 32nd Congress of the International Union of Physiological Sciences, Glasgow, 355.2/P (Month?)

Wang C, Dreher B, Burke W (1993) Receptive-field related inhibition of X-lagged cells in the dorsal lateral geniculate nucleus of the cat. Sensory Stratagems: 1993 Robertson Symposium, Canberra (Feb)

Burke W, Wang C, Dreher B (1993) The role of the Y system in non-dominant suppression in the dorsal lateral geniculate nucleus of the cat. Sensory Stratagems: 1993 Robertson Symposium, Canberra (Feb)

Dreher B, Djavadian RL, Wang C, Turlejski K, Burke W (1993) Area 21a and PMLS of cat visual cortex constitute two distinct areas: Hodological and functional evidence. Sensory Stratagems: 1993 Robertson Symposium, Canberra (Feb)

1993 PHYSIOLOGY REPORT - BURKE