Localization of the human female breast in primary somatosensory cortex

Rationale: Despite an extensive body of research on the topography of the primary somatosensory cortex (S1) little is known about the representation of the trunk. Aim: The aim of this study was to determine the representation of the breast in S1 in human females. Results: The representation of the human breast in primary somatosensory cortex was determined in ten healthy female subjects. Non-painful electrical stimulation of the mammilla (Th4 dermatome), groin (L1 dermatome) and the first digit of both sides of the body activated cutaneous receptors and thus elicited somatosensory evoked potentials. The representation of these body parts in primary somatosensory cortex (S1) was determined using neuroelectric source imaging. Equivalent current dipole localizations were overlaid with individual structural magnetic resonance images to account for individual cortical differences. The breast representation was localized between the representation of the groin and the first digit. In the medial–lateral direction the representation of the breast was approximately 15 mm lateral of the longitudinal fissure in the contralateral hemisphere. Source localizations were stable across subjects. However, one subject showed ipsilateral representation of the breast, which might be related to bilateral receptive fields of the ventral body midline representation. This study confirms the Penfield and Rasmussen (1950) invasive data by use of noninvasive source imaging.     

Reliability and validity of neuroelectric source imaging in primary somatosensory cortex of human upper limb amputees

The present study investigated the test-retest reliability of EEG source localizations of somatosensory evoked potentials (SEPs) in human upper limb amputees over a long time frame (several months) and examined the validity of source reconstruction. In two sessions spaced several months apart five unilateral upper limb amputees were stimulated at the first and fifth digit of the intact hand and at the left and right lower corner of the mouth. To examine the validity of the results of the neuroelectric source reconstruction a comparison with neuromagnetic source localization was performed for two subjects. The source localizations of the SEP components were found to be highly reproducible: the mean standard deviation of the dipole locations was 8.80 mm in the x-, 7.00 mm in the y- and 4.15 mm in the z-direction. The match of the comparison of EEG and MEG data was in the range of one centimeter. These results support the use of multi-electrode EEG recordings combined with MRI as an adequate method for the investigation of the functional organization of the somatosensory cortex in upper limb amputees and suggest high stability of cortical reorganization in these subjects.     

Retrieval and emotional processing of traumatic memories in posttraumatic stress disorder: peripheral and central correlates

Posttraumatic stress disorder (PTSD) is thought to be characterized by dysfunctional memory processes, i.e., the automatic re-experiencing of the traumatic event and the inability to consciously recall facts about the traumatic event, as well as altered emotional processing of trauma-relevant cues. The present study examined the cerebral mechanisms underlying the cued recall of trauma-specific memories and the emotional processing of the presented cues in 16 PTSD patients, 15 trauma-exposed subjects without PTSD and 16 healthy controls. Subjects received questions about their specific trauma as well as other disastrous and neutral events while the electroencephalogram and heart rate were measured. The PTSD patients showed no impairment in trauma-specific declarative memory compared to non-PTSD subjects but had some deficits in general declarative memory as assessed by the Wechsler Memory Scale-Revised. Compared to healthy control subjects, PTSD patients displayed increased P300 and late positive complex amplitudes to trauma-specific questions, indicating enhanced emotional processing of these cues. In line with their behavioral performance, both trauma-exposed groups showed decreased terminal contingent negative variation amplitudes to trauma-specific questions over frontal electrodes reflecting altered memory retrieval. Within-group comparisons revealed that only the PTSD group but not the other groups showed a differentiation between trauma-specific and neutral questions with respect to the LPC, tCNV and P300. Concordantly with previous studies, PTSD patients showed elevated resting heart rate compared to the healthy controls. These findings are discussed in the context of current models of the role of declarative memory in the development and maintenance of PTSD.     

Einstellungen zu alten Menschen zu Beginn und am Ende des Medizinstudiums

In the present study, 188 first year and 120 sixth year students of the University of Zurich were questioned about their attitudes towards older people, their knowledge concerning aging specific developments, their experiences with older people and their own expectations concerning old age. Structured and standardized questionnaires were used. The data were analyzed using univariate and multivariate statistical methods. The results show a positive image of old age independent of gender and point in time of education. Their positive experiences with older people and their positive expectations concern their own aging refer, above all, to their own mental health. For the transfer of gerontological and geriatric knowledge in the education of medical students, these mainly positive attitudes towards older people should be taken into account. Risk factors as well as protective factors concerning the development and treatment of diseases which are characteristic for old age should be pointed out.