Temporal lobe stimulations and seizures

The dreamy state: hallucinations of autobiographic memory evoked by temporal lobe stimulations and seizures
Using results from cortical stimulations, as well as the symptoms of spontaneous epileptic seizures recorded by stereoelectroencephalography we re-studied the phenomenon of the dreamy state. A total of 15 sensations of déjà vécu, 35 visual hallucinations consisting of the image of a scene and 5 'feelings of strangeness' occurred. These were recorded during 40 stimulations in 16 subjects, and 15 seizures in 5 subjects. Forty-five per cent of dreamy states were evoked by stimulation of the amygdala, 37.5% by the hippocampus and 17.5% by the para-hippocampal gyrus. During both spontaneous and provoked dreamy state, the electrical discharge was localized within mesial temporal lobe structures, without involvement of the temporal neocortex. Early spread of the discharge to the temporal neocortex appeared to prevent the occurrence of the dreamy state. Semiological analysis showed a clinical continuity between déjà vécu and visual hallucinations, the latter often consisting of a personal memory that was 'relived' by the subject; such memories could be recent, distant or from childhood. With one exception, the particular memory evoked differed from one seizure to another, but were always drawn from the same period of the subject's life. Given the role of the amygdala and hippocampus in autobiographic memory, their pathological activation during seizures may trigger memory recall. This study of the dreamy state is in keeping with other evidence demonstrating the constant and central role of the amygdala and hippocampus (right as much as left) in the recall of recent and distant memories. It demonstrates the existence of large neural networks that produce recall of memories via activation of the hippocampus, amygdala and rhinal cortex.
Source: Brain. 2007 Jan ; 130(Pt 1): 88-99

Single Neuronal Activity during Unstructured Arm Movements

Tyson N. Aflalo and Michael S. A. Graziano

It comes as no surprise that movements in monkeys are accompanied by single neuronal activity in the motor cortex, but it is less clear which motor parameters are most critical. For example, is it spatial, joint-based, or muscle-based? To get at this question, Aflalo and Graziano let monkeys do their own thing, thus removing the potentially confounding contribution of overly constrained movements in highly trained animals. The authors measured spontaneous arm movements in untrained monkeys using a threedimensional tracking system and recorded from individual neurons in motor cortex. As expected from studies in restrained animals, standard tuning properties of motor cortex neurons were present. Neurons were tuned to multiple movement parameters. The total variance in neuronal activity reflected hand speed (1%), hand direction (8%), complex directional tuning (13%), final hand position (22%), and final arm posture (36%). The authors propose that these rankings reflect the importance of each parameter to arm movements.
Society for Neuroscience