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L Leinonen

Publications and source records attributed to L Leinonen.

42 records · Page 3Linked to original sources
PubMed1978

Effect of ethanol on neuronal activity in the parietal association cortex of alert monkeys.

The effect of alcohol was studied in alert monkeys on the cellular mechanisms of the posterior parietal association cortex, a region that normally participates in visuo-spatial co-ordination of hand movements. In thirty-two experiments, the effects of intracardiac administration of ethanol were monitored by the intracortical multiple-unit recording technique. Alcohol produced rhythmic groupings of the spontaneous impulse activity; the rhythm was accentuated by closing the eyes. The dominant frequency of this rhythm (3.5 to 1 Hz) correlated inversely with the blood alcohol level. Three groups of response types were studied in Brodmann's area 7. At 8 of 12 recording sites, a close correlation was observed between the monkey's reaching accuracy and the magnitude of integrate multineuronal responses to reaching with the contralateral arm under visual guidance, or to grasping an object. Half of the 10 recording sites which were activated by complex visual stimulation also showed a close correlation with the behavioural action of alcohol. Least sensitive to alcohol were somatosensory responses; only 3 of 10 of such recording sites were influenced by moderate doses of alcohol. Larger doses producing coma increased the proportion of responses blocked by alcohol, whereas no effects were observed in the adjacent primary somatosensory cortex. Our results show that the posterior parietal association cortex is very sensitive to the action of alcohol. Moreover, these findings support the theory that the action of alcohol in various parts of the central nervous system depends on the complexity of synaptic contacts to the location under study.

Action Potentials↗
PubMed1978

Modification of visual functions of the parietal lobe at early age in the monkey.

In addition to the visual pathway ending in the visual cortex, visual information is also processed in the associative areas of the cortex. We have studied the posterior parietal association area (Brodmann's area 7), and in our sample about 40% of the neurons were influenced by visual stimulation or ocular movements. The visually activated neurons in this region in normal adult monkeys have large, binocular receptive fields and they respond well to all moving visual stimuli near the animal. They do not differentiate between different patterns of visual stimuli but respond well to objects of interest, such as food, drinks, new objects, etc. Many visual neurons also respond to somatic stimulation. Preliminary experiments on two young monkeys suggest that the visual input into area 7 is strongly modified by early visual deprivation. In one monkey monocular deprivation lead to total absence of any influence from the deprived eye to area 7. No deprivation effect was observed in the lateral geniculate nucleus of the thalamus and the effect in area 7 was stronger than in the visual cortex (area 17). One monkey raised with bilateral eye closure was behaviourally blind after the opening of the eyes and remained so for the observation period of one month. In area 7 of this monkey the proportion of recording sites responsive to visual stimulation was sharply reduced. In kittens binocular deprivation is known to effect the function of the visual cortex much less than monocular deprivation. It seems possible that at early age inputs representing different sensory systems compete for influence in the associative cortical areas in the same way as there is competition between inputs from the two eyes to the visual cortex.

Age Factors↗
PubMedDate not supplied

Cortical sensory evoked potentials and communicative forebrain functions.

Cortical evoked potentials were measured to visual, auditory and somatosensory stimuli in 20 subjects with serious neurodevelopmental impairments due to various etiologies. The results were compared with behavioral observations to find out whether the absence/presence of the responses corresponded to the level of social functioning. No cortical evoked potentials were elicited in two subjects, responses to the stimulation of one modality were missing in three subjects (retinal b-waves and brainstem auditory and somatosensory evoked potentials were, however, preserved in them). No communicative behavior was observed in subjects with absent responses. Ten subjects had marked deviations in the evoked potentials, the behavioral observations in them, ranging from no communication to sentenced speech. Five subjects had normal response patterns and they showed a great variety of communicative skills, including speech. The results support the view that bilateral loss of cortical somatosensory, visual, and auditory evoked potentials is a sign of loss of neural substrates of communication.

Adolescent↗