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Does transcranial magnetics stimulation influence memory?
s43 EEG COHERENCE COMPUTED FROM LAPLACIAN RECORDINGS: R@HJLTS FOR VERBAL AND SPATIAL TASKS AND FOR A RESTING EYES-OPEN CONDITION. G. Fe-in and C. Biggins (University
of California,
San Francisco,
CA, U.S.A.)
EEG coherence measurements computed from common reference recordings are subject to confounding by power and phase effects at the reference and recording electrodes. In the context of this potential problem, we have suggested that coherence should be computed from reference free recordings. We will present EEG coherence data computed from such recordings during both resting and active tasks. For 10 adult, right-handed subjects, we collected 24 channel EEG recordings during a resting eyes-open condition and during verbal and spatial tasks which were equated for task difficulty. The verbal and spatial tasks involved considerable eye movement and we implemented frequency domain eye movement contamination removal algorithms for the horizontal and vertical EOG. We used spline interpolation to generate a differentiable estimate of the potential surface over the scalp. We computed the second spatial derivative of the spline function at each electrode location as an estimate of the current source density at that site. Coherence was computed between these estimates of the (reference-free) current source density. The results will be presented as they pertain to: (1) evidence for long fiber connections between cortical areas; (2) differences between verbal and spatial tasks; and (3) differences between resting and active conditions. The results of the eye movement contamination removal procedures will also be presented in detail.
BRAIN-STEM AUDITORY EVOKED POTENTIALS (BAEP) AND SOMATOSENSORY EVOKED POTENTIALS (SEP) IN PONTINE HEMORRHAGE. A. Ferberf, H. Buchner (RWTH,
Aachen,
and H. Briickmann
F.R.G.)
Electrophysiological studies were carried out on 17 patients with pontine hemorrhage. Most of the patients suffered massive hypertensive bleeding leading to death in twelve of them within three months. Of the five remaining patients, two had a bad outcome and three a fairly good outcome. BAEP and SEP were recorded in all patients, mostly with serial recordings. BAEP were pathological in all patients. The most important finding was a reduction in amplitude or loss of waves. All patients with a bilateral loss of waves after wave II died; the two patients with normal amplitude of waves I-V at least on one side survived in good condition. Further prognostic conclusions were not possible. The correlation to clinical state was limited and found to be best with a small unilateral tegmental bleeding.
Eleven of the 17 patients suffered bilateral loss of the N20 component of the median nerve SEP. All of these patients died. In patients with unilateral loss of SEP the outcome could be favorable even if the bleeding extended over the midline. ‘Subcortical’ SEP were not significantly changed. EEG findings in 15 and VEP in four patients showed preserved electrical activity of the forebrain, even in patients in poor condition.
DOES TRANSCRANIAL FLUENCE MEMORY? A. Ferbert, Buchner (RWTH,
N.
Aachen.
MAGNETIC STIMULATION
Mussmann,
A. Menne,
W. Hartje
and
IN-
H.
F.R.G.)
Using the new technique of transcranial magnetic stimulation (TCMS) for evaluation of the motor pathways. it is not yet possible to achieve a very focal stimulation of the motor cortex. Therefore, higher functions of the CNS may be influenced by such a test. We attempted to answer the question whether short-term memory is disturbed during routine TCMS. We investigated 31 healthy students (20-28 years). Nonsense German words were presented (e.g., Reubal. Zepnig) shortly before a magnetic stimulus, with a coil positioned over the vertex. Three blocks each containing 6 words were presented, each followed by a magnetic stimulus. Thus, there were 18 test words and 18 magnetic stimuli. The intensity of the magnetic field in the three blocks was 60, 80, and 100% of the maximum field. After each block the subject was requested to give a free reproduction of the 6 words. After finishing the third block there was an additional multiple choice test for correct recognition of the 18 words. 18 subjects were stimulated with the above mentioned field intensities (test group) whereas 13 subjects had 0% ‘stimulation’ using an otherwise identical test setting (control group). There were no significant differences between the test group and the control group concerning free reproduction in the three blocks. Similarly, in the multiple choice test, there was no significant difference in correct recognition of the words between the two groups. According to our results, there is no influence of transcranial magnetic stimulation on shortterm memory in a setting used for the investigation of motor pathways.
CARDIAC AUTONOMIC SLEEP IN DIABETICS.
DYSFUNCTION
L. Fermi-Strambi, Franreschi
P. Pinto.
(Institute
S. Smirne,
S. Raffaele,
Milan,
Heart rate (HR) variations response to specific stimuli,
M. Zucconi
DURING
and
M.
Italy) during wakefulness, at rest, or in are often used to assess autonomic
of California,
San Francisco,
CA, U.S.A.)
EEG coherence measurements computed from common reference recordings are subject to confounding by power and phase effects at the reference and recording electrodes. In the context of this potential problem, we have suggested that coherence should be computed from reference free recordings. We will present EEG coherence data computed from such recordings during both resting and active tasks. For 10 adult, right-handed subjects, we collected 24 channel EEG recordings during a resting eyes-open condition and during verbal and spatial tasks which were equated for task difficulty. The verbal and spatial tasks involved considerable eye movement and we implemented frequency domain eye movement contamination removal algorithms for the horizontal and vertical EOG. We used spline interpolation to generate a differentiable estimate of the potential surface over the scalp. We computed the second spatial derivative of the spline function at each electrode location as an estimate of the current source density at that site. Coherence was computed between these estimates of the (reference-free) current source density. The results will be presented as they pertain to: (1) evidence for long fiber connections between cortical areas; (2) differences between verbal and spatial tasks; and (3) differences between resting and active conditions. The results of the eye movement contamination removal procedures will also be presented in detail.
BRAIN-STEM AUDITORY EVOKED POTENTIALS (BAEP) AND SOMATOSENSORY EVOKED POTENTIALS (SEP) IN PONTINE HEMORRHAGE. A. Ferberf, H. Buchner (RWTH,
Aachen,
and H. Briickmann
F.R.G.)
Electrophysiological studies were carried out on 17 patients with pontine hemorrhage. Most of the patients suffered massive hypertensive bleeding leading to death in twelve of them within three months. Of the five remaining patients, two had a bad outcome and three a fairly good outcome. BAEP and SEP were recorded in all patients, mostly with serial recordings. BAEP were pathological in all patients. The most important finding was a reduction in amplitude or loss of waves. All patients with a bilateral loss of waves after wave II died; the two patients with normal amplitude of waves I-V at least on one side survived in good condition. Further prognostic conclusions were not possible. The correlation to clinical state was limited and found to be best with a small unilateral tegmental bleeding.
Eleven of the 17 patients suffered bilateral loss of the N20 component of the median nerve SEP. All of these patients died. In patients with unilateral loss of SEP the outcome could be favorable even if the bleeding extended over the midline. ‘Subcortical’ SEP were not significantly changed. EEG findings in 15 and VEP in four patients showed preserved electrical activity of the forebrain, even in patients in poor condition.
DOES TRANSCRANIAL FLUENCE MEMORY? A. Ferbert, Buchner (RWTH,
N.
Aachen.
MAGNETIC STIMULATION
Mussmann,
A. Menne,
W. Hartje
and
IN-
H.
F.R.G.)
Using the new technique of transcranial magnetic stimulation (TCMS) for evaluation of the motor pathways. it is not yet possible to achieve a very focal stimulation of the motor cortex. Therefore, higher functions of the CNS may be influenced by such a test. We attempted to answer the question whether short-term memory is disturbed during routine TCMS. We investigated 31 healthy students (20-28 years). Nonsense German words were presented (e.g., Reubal. Zepnig) shortly before a magnetic stimulus, with a coil positioned over the vertex. Three blocks each containing 6 words were presented, each followed by a magnetic stimulus. Thus, there were 18 test words and 18 magnetic stimuli. The intensity of the magnetic field in the three blocks was 60, 80, and 100% of the maximum field. After each block the subject was requested to give a free reproduction of the 6 words. After finishing the third block there was an additional multiple choice test for correct recognition of the 18 words. 18 subjects were stimulated with the above mentioned field intensities (test group) whereas 13 subjects had 0% ‘stimulation’ using an otherwise identical test setting (control group). There were no significant differences between the test group and the control group concerning free reproduction in the three blocks. Similarly, in the multiple choice test, there was no significant difference in correct recognition of the words between the two groups. According to our results, there is no influence of transcranial magnetic stimulation on shortterm memory in a setting used for the investigation of motor pathways.
CARDIAC AUTONOMIC SLEEP IN DIABETICS.
DYSFUNCTION
L. Fermi-Strambi, Franreschi
P. Pinto.
(Institute
S. Smirne,
S. Raffaele,
Milan,
Heart rate (HR) variations response to specific stimuli,
M. Zucconi
DURING
and
M.
Italy) during wakefulness, at rest, or in are often used to assess autonomic