Effects of Subcortical Lesions on Cortical Electroencephalogram in Cats

Abstract

of experiments to be presented here the ef¬ fects of lesions in various parts of the thalamus, internal capsule, and caudate nu¬ cleus, and, to some extent, in the midbrain, on cortical potential patterns were studied. METHODSElectrolytic lesions were produced stereotactically in selected regions of the thalamus, midbrain, internal capsule, and caudate nu¬ cleus in 35 cats. Postoperative observations of general behavior and responsiveness were made over periods ranging from one week to several months. Cortical potentials were recorded through silver electrodes fastened into holes in the skull with acrylic plastic, the lead wires be¬ ing soldered to the electrodes, which were in contact with the dura in either the frontal or the occipital region. These leads were placed in a preliminary operation. Usually eight contact points were available. A fourchannel electroencephalograph was used for most observations; a Grass Model III eightchannel instrument and a low-frequency an¬ alyzer were, in some instances, also employed in recording cortical potentials.After implantation of the electrodes and operative healing, several prelesion EEG's were taken, at intervals of several days, until it was certain the potential patterns were stable and sufficient information as to bilateral matching was secured. The animals were then reoperated on under pentobarbital (Nembutal) anesthesia, and the lesions were produced, using a craniotomy opening pre¬ pared at the time of the first operation. Re¬ covery was usually rapid. Records were taken soon after recovery from the anesthesia and at intervals thereafter until normal po¬ tentials appeared or until the postoperative patterns stabilized. These recording periods were long enough to permit the animal to Downloaded From: http://archneurpsyc.jamanetwork.com/ by a University of British Columbia Library User on 06/19/2015

Cortical metabolism in posterolateral thalamic stroke: PET study

“…Thus, somatosensory stimulations in humans increase blood flow and metabolism in the contralateral SM cortex (36) and electric stimulation of the VPL in both humans and rats results in metabolic activation in the SM area (37,38). In addition, numerous experimental findings have established that the specific cortical projections are anatomically and functionally independent from the non-specific system (31,32,35,(39)(40)(41). Hence, the lack of diffuse ICH in our study further emphasizes the major impact of the non specific thalamo-cortical system on resting cortical metabolism.…”

Diaschisis.

“…45 "" These effects, which depending on the size of the lesion last for weeks or longer, reportedly affect the entire ipsilateral cortical mantle. Lesions of a "specific" projection nucleus, such as the ventral-posterior-lateral nucleus may not result in EEG slowing or die effects are restricted to the somatosensory cortical projection area.…”

“…Lesions of a "specific" projection nucleus, such as the ventral-posterior-lateral nucleus may not result in EEG slowing or die effects are restricted to the somatosensory cortical projection area. 45 ' ** Unilateral lesions of the rostral pole of the thalamus (anterior-ventral and reticular nuclei) in the cat, depressed both seizure activity and sleep spindles over the ipsilat-eral cortical hemisphere without attenuating cortical evoked responses. This suppression of cortical circuitry involved in the generation of synchronous discharge without reducing cortical excitability can be considered a selective remote cortical effect of injury to the anterior thalamus.…”

“…The effects of experimentally induced caudate lesions in animals were mild, transient and not reproducible by similar putamenal lesions. 45 ' "* Of the few anecdotal reports of patients with stroke involving the striatum, none were "pure," but also involved adjacent internal capsule and hence possibly thalamo-cortical fibers. In these cases, mild metabolic depression affecting the entire ipsilateral cortical mantle and thalamus, has been described.…”

Evolution of Seizure Patterns in Experimental Epilepsy

“…They illustrate an EEG in which a generalized myoclonic jerk accompanied regularly spaced spikes in the EEG. Knott et al [39] stated that one cat with a bilaterally symmetrical electrolytic midbrain lesion showed spon taneous spikes on the 4th day accompanied by slight myoclonic jerking. Also of interest is that in the cat under chloralose anesthesia a suddenly applied stimulus, visual, acoustic, or somesthctic, evokes a generalized myoclonic reaction [40].…”