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Developmental changes of central conduction time of somatosensory pathway in neonates, infants and children
The N20 peak amplitude was somewhat higher with faster displacements (-0.3 @1! -0.3 FV, and -0.5 $Lv. respectively) and the latencies were significantly shorter i25.0 rns, 23.4 ms, and 21.5 ms, respectively). The P25 amplitude was somewhat lower to ,faster displacements (1.5 PV, 1.2 WV, and 1.I fiLv.respectively), the latencies were shorter (34.6 ms, 30.4 ms. and 28.7 ms, respectively). The N35 wave was obvious in two volunteers only with the absolute amplitude around 0 ~Vand latencies 42.3 ms, 39.5 ms. and 36.6 ms. respectively. The P45 peak amplitude was around + 1 .O PV and latencies; 49.5 ms, 46.4 ms and 43.6 ms, respective@. The peak amplitudes of these waves were to electrical stimulation of the median nerve at the motor threshold at the wrist much higher than to the fastest mechanical stimulation, while the !atencies were oniy 1 to 3 ms shorter. it seems therefcre. that only a portion of the afferent fibres capable to actrvate the elements of the primary somatosensory cortex was activated by the skin displacement of 350 pm. We believe that these were afferents of the skin origin only. It seems that possibilities to manipulate the characteristics of the somatosensory input by means of well controlled quantified mechanical stimulation are offering wide possibilities to study functioning of the somatosensory system also in pathologic conditions.
45-j 1 Analya~~ L-i__.l stimulation
of Brainstem
Responses to Upper Limb by Means of Combined Scalp and aso~~~rin~~ai Recordings
D. Restuccia, V Di Lazzaro. M Valeriani. P Tonali. Cafholic University Roma We studied upper limb SEPs in 10 healthysubjects by means of simultaneous surface recordings around the neck at the C6 level and on the scalp over the parietal and froniai regions; furthermore, to better analyze the brainstem components, a circular array was positioned at the level of C2. using a nasopharingeal (NP) electrode to record evoked responses nearby the ventral surface of the brainstem. Reference electrode was always positioned on a non-cephalic site. Scalp and NP recordings enabled us to recognize two distinct potentials in the 14 ms range of latency, labelled as “P13” and “P14.” In scalp recordings, the PI4 component was larger than the P13, as in previous studies {Yamada et al.. 1986). Conversely, in NP recordings the PI3 component was greater than the PI4 and often it was the only measurable brainstem response. Neither the PI3 nor the PI4 component showed a clear-cut phase reversal between C2 and Np; furthermore, the latency of both components remained unchanged in scalp and NP recordings, confirming that both responses are not generated by a stationary horizontal dipole. We studied, with the same technique, 2 patients with a lower brainstem lesion and one patien? with a lesion of the cervico-medullary junction. In the first two patients, NP recording revealed the preservation of the PI3 component, in spite of the abolition of the P14 far-field. In the third patient, both PI3 and PI4 responses were absent on scalp and NP recordings, in spite of the preservation of the cervical N13. Our preliminary data suggest that the combined utilization of Np and scalp recordings could be a reliable diagnostic tool in disclosing brainstem lesions with P13-P14 dissociation.
j 45-12
j S~matos~~s~~y to a Body Sire
Central Conduction
ii. Takada, r. Ozaki. M. Baba, M. Matsunaga.
Time Correlates
University of Hirosaki, Hirosaki
Generally the somatosensorycentral conduction time (peak CCT) is measured from the peak of the cervica! “N13” component to the peak of the cortical N20 component in the contralateral parietal scalp (PC) using Fz montage. However, the cervical component recorded from the posterior neck (cv6) may be modiiied by Fz reference which subtracts the brain stem PI4 from a true spinal N13 potential. Another determination of CCT (onset CCT) is to measure from the onset of the PI 1 component corresponds to spinal entryto the onset of the N20 component, which is known to be unchanged regardless a choice of reference. We compared the two methods for somatosensory CCT to analyze cervical SEFs recorded from the anterior and posterior neck and scalp SEPs from Fz and PO with noncephalic reference in 72 normal adults whose height ranged from 142 to 190 cm. Electronic subtraction offered cervical “N13” in cv6-Fz montage. There was not significant difference between “N13” peak latency and PI4 peak latency of scalp SEPs. suggesting the peak CCT indicates interpeak latency between P14 and NZO. N20 duration varied much among individuals, so that peak CCT did not correlate with height. On the other hand, there was a significant correlation between onset CCT and height (p < 0.0001). It is, therefore, favorable to apply the onset CCT for clinical use
since onset CCT reflects the transit time of the somatosensory spinal entry to parietal receiving cortex.
145-l
volley from
3 1 Short Latency Somatosensory Ev Recorded Around the Human ~~~~~
E. Urasaki *, S. Johns Hopkins Johns Hopkins Institute, Johns
tiematsu *, R.P Lesser*. *Departmen~ofNeurosurgery University School of Medicine; **Department of Neurolog)i University School of Medicine and Zanvyl Krieger MindjErain Hopkins University
We analyzed the intracranial spatiotemporai drstributions of the N18 component of short latency somatosensory evoked potentials (SSEPs) in three patients with epilepsy. In these patients, depth electrodes were implanted bilaterally into the frontal and temporal lobes, with targets including the amygdala and hippocampus; the latter two targets are close to the upper pons and midbrain. In this study N18 was divided into the initial negative peak (Nl8a) and the following prolonged negativity (N18b). Mapping around the upper pons and midbrain showed that: (1) the amplitude of the first negativity, which coincided with scalp N18a. was larger contralateral to the side of stimulation, but showed no polarity change around the upper brainstem; and (2) the second negativity, which was similar to scalp Ni8b, did show an amplitude difference or a polarity change. This wave appeared to reflect a positive-negative dipole directed in a dorso-ventral as we)) as dorso-fateral direction from the midbrain, where positivity arises from ?he dorsum of the midbrain, contralateral to the side of the stimulation. Recordings from depth electrode derivations oriented in a caudo-rostra1 direction suggest that N18a and N18b may in part reflect neural activity originating from the upper pons to midbrain region which projects to the rostra1 subcortical white matter of the frontal lobe as stationary peaks.
145-l
4 1 Developmental Changes of ~sfl~~a~ d~~t~o~ 7-l of Somatosensory Pathway in ~e~~~~es, ~nf~~t~ an Children
A. Yasuhara, A. Araki, Y. Tian, N. Kitamura. Y Kobayashi. i(ansaiMedica/ UniversiN Moriguchi. Osaka, Japan The central conduction time (CCT) is the latency difference between the PI 4 of the somatosensory evoked potentials (SEP) and the cortica) SEP (N20). To investigate the developmental change of CCT to median nerve stimulation, SEP were recorded in 135 infants and children from the premature infants to 18 years of age. Mean CCT was 14.7 msec in the premature infants and remained unchanged during the neonatal period. After 43 weeks of conception, CCT gradually decreased to the adult level at 9 years of age. which was 6.4 msec. By dividing CCT into 2 parts, the latency between N18 and N20 (CCT2) was longer than CCTI. which was the latency between P14 and NT8 during the neonatal period. CCTZ decreased quickly afterone month of age and became shorter than CCTI after 5 or 6 months of age. At the same period the rapid myelination was observed by MRI in the somatosensory area of the cortex, The maturation of CCT starts from the caudal brainstem to the central part. The maturation of CCT2 might be related to the myelination of the somatosensory cortex.
SESSION
146-01 1Asymmetrical Event-Related Lobectomy
46: P300 - 2
Change in P308 Potentials After
Y. Hirayasu, H. Ohta, K. Fukao, C. Ogura, J, Mukawa. Unwersily of the Ryukyus, Okinawa, Japan Abnormality in P300 of event-related potentia!s (ERPs) has beern reported in several psychiatric diseases. However, the source of this component remains unclear. Intracranial recordings from the media! temporal lobe have demonstrated the seizable oddball-sensitive ERP wave, which appears to be locally generated. These findings suggests that P300 is generated in the medial temporal lobe. Therefore, removal of this area should affect the distribution of P300. However, literatures on ERPs for the patients with temporal lobectomy have failed to show, P300 asymmetry. In this study, we
45-j 1 Analya~~ L-i__.l stimulation
of Brainstem
Responses to Upper Limb by Means of Combined Scalp and aso~~~rin~~ai Recordings
D. Restuccia, V Di Lazzaro. M Valeriani. P Tonali. Cafholic University Roma We studied upper limb SEPs in 10 healthysubjects by means of simultaneous surface recordings around the neck at the C6 level and on the scalp over the parietal and froniai regions; furthermore, to better analyze the brainstem components, a circular array was positioned at the level of C2. using a nasopharingeal (NP) electrode to record evoked responses nearby the ventral surface of the brainstem. Reference electrode was always positioned on a non-cephalic site. Scalp and NP recordings enabled us to recognize two distinct potentials in the 14 ms range of latency, labelled as “P13” and “P14.” In scalp recordings, the PI4 component was larger than the P13, as in previous studies {Yamada et al.. 1986). Conversely, in NP recordings the PI3 component was greater than the PI4 and often it was the only measurable brainstem response. Neither the PI3 nor the PI4 component showed a clear-cut phase reversal between C2 and Np; furthermore, the latency of both components remained unchanged in scalp and NP recordings, confirming that both responses are not generated by a stationary horizontal dipole. We studied, with the same technique, 2 patients with a lower brainstem lesion and one patien? with a lesion of the cervico-medullary junction. In the first two patients, NP recording revealed the preservation of the PI3 component, in spite of the abolition of the P14 far-field. In the third patient, both PI3 and PI4 responses were absent on scalp and NP recordings, in spite of the preservation of the cervical N13. Our preliminary data suggest that the combined utilization of Np and scalp recordings could be a reliable diagnostic tool in disclosing brainstem lesions with P13-P14 dissociation.
j 45-12
j S~matos~~s~~y to a Body Sire
Central Conduction
ii. Takada, r. Ozaki. M. Baba, M. Matsunaga.
Time Correlates
University of Hirosaki, Hirosaki
Generally the somatosensorycentral conduction time (peak CCT) is measured from the peak of the cervica! “N13” component to the peak of the cortical N20 component in the contralateral parietal scalp (PC) using Fz montage. However, the cervical component recorded from the posterior neck (cv6) may be modiiied by Fz reference which subtracts the brain stem PI4 from a true spinal N13 potential. Another determination of CCT (onset CCT) is to measure from the onset of the PI 1 component corresponds to spinal entryto the onset of the N20 component, which is known to be unchanged regardless a choice of reference. We compared the two methods for somatosensory CCT to analyze cervical SEFs recorded from the anterior and posterior neck and scalp SEPs from Fz and PO with noncephalic reference in 72 normal adults whose height ranged from 142 to 190 cm. Electronic subtraction offered cervical “N13” in cv6-Fz montage. There was not significant difference between “N13” peak latency and PI4 peak latency of scalp SEPs. suggesting the peak CCT indicates interpeak latency between P14 and NZO. N20 duration varied much among individuals, so that peak CCT did not correlate with height. On the other hand, there was a significant correlation between onset CCT and height (p < 0.0001). It is, therefore, favorable to apply the onset CCT for clinical use
since onset CCT reflects the transit time of the somatosensory spinal entry to parietal receiving cortex.
145-l
volley from
3 1 Short Latency Somatosensory Ev Recorded Around the Human ~~~~~
E. Urasaki *, S. Johns Hopkins Johns Hopkins Institute, Johns
tiematsu *, R.P Lesser*. *Departmen~ofNeurosurgery University School of Medicine; **Department of Neurolog)i University School of Medicine and Zanvyl Krieger MindjErain Hopkins University
We analyzed the intracranial spatiotemporai drstributions of the N18 component of short latency somatosensory evoked potentials (SSEPs) in three patients with epilepsy. In these patients, depth electrodes were implanted bilaterally into the frontal and temporal lobes, with targets including the amygdala and hippocampus; the latter two targets are close to the upper pons and midbrain. In this study N18 was divided into the initial negative peak (Nl8a) and the following prolonged negativity (N18b). Mapping around the upper pons and midbrain showed that: (1) the amplitude of the first negativity, which coincided with scalp N18a. was larger contralateral to the side of stimulation, but showed no polarity change around the upper brainstem; and (2) the second negativity, which was similar to scalp Ni8b, did show an amplitude difference or a polarity change. This wave appeared to reflect a positive-negative dipole directed in a dorso-ventral as we)) as dorso-fateral direction from the midbrain, where positivity arises from ?he dorsum of the midbrain, contralateral to the side of the stimulation. Recordings from depth electrode derivations oriented in a caudo-rostra1 direction suggest that N18a and N18b may in part reflect neural activity originating from the upper pons to midbrain region which projects to the rostra1 subcortical white matter of the frontal lobe as stationary peaks.
145-l
4 1 Developmental Changes of ~sfl~~a~ d~~t~o~ 7-l of Somatosensory Pathway in ~e~~~~es, ~nf~~t~ an Children
A. Yasuhara, A. Araki, Y. Tian, N. Kitamura. Y Kobayashi. i(ansaiMedica/ UniversiN Moriguchi. Osaka, Japan The central conduction time (CCT) is the latency difference between the PI 4 of the somatosensory evoked potentials (SEP) and the cortica) SEP (N20). To investigate the developmental change of CCT to median nerve stimulation, SEP were recorded in 135 infants and children from the premature infants to 18 years of age. Mean CCT was 14.7 msec in the premature infants and remained unchanged during the neonatal period. After 43 weeks of conception, CCT gradually decreased to the adult level at 9 years of age. which was 6.4 msec. By dividing CCT into 2 parts, the latency between N18 and N20 (CCT2) was longer than CCTI. which was the latency between P14 and NT8 during the neonatal period. CCTZ decreased quickly afterone month of age and became shorter than CCTI after 5 or 6 months of age. At the same period the rapid myelination was observed by MRI in the somatosensory area of the cortex, The maturation of CCT starts from the caudal brainstem to the central part. The maturation of CCT2 might be related to the myelination of the somatosensory cortex.
SESSION
146-01 1Asymmetrical Event-Related Lobectomy
46: P300 - 2
Change in P308 Potentials After
Y. Hirayasu, H. Ohta, K. Fukao, C. Ogura, J, Mukawa. Unwersily of the Ryukyus, Okinawa, Japan Abnormality in P300 of event-related potentia!s (ERPs) has beern reported in several psychiatric diseases. However, the source of this component remains unclear. Intracranial recordings from the media! temporal lobe have demonstrated the seizable oddball-sensitive ERP wave, which appears to be locally generated. These findings suggests that P300 is generated in the medial temporal lobe. Therefore, removal of this area should affect the distribution of P300. However, literatures on ERPs for the patients with temporal lobectomy have failed to show, P300 asymmetry. In this study, we