RESUMO
BACKGROUND: Prepulse inhibition (PPI) of the acoustic startle response, a measurement of sensorimotor gaiting, is modulated by monoaminergic, presumably dopaminergic neurotransmission. Disturbances of the dopaminergic system can cause deficient PPI as found in neuropsychiatric diseases. A target specific influence of deep brain stimulation (DBS) on PPI has been shown in animal models of neuropsychiatric disorders. In the present study, three patients with early dementia of Alzheimer type underwent DBS of the median forebrain bundle (MFB) in a compassionate use program to maintain cognitive abilities. This provided us the unique possibility to investigate the effects of different stimulation conditions of DBS of the MFB on PPI in humans. RESULTS: Separate analysis of each patient consistently showed a frequency dependent pattern with a DBS-induced increase of PPI at 60 Hz and unchanged PPI at 20 or 130 Hz, as compared to sham stimulation. CONCLUSIONS: Our data demonstrate that electrical stimulation of the MFB modulates PPI in a frequency-dependent manner. PPI measurement could serve as a potential marker for optimization of DBS settings independent of the patient or the examiner.
Assuntos
Doença de Alzheimer/fisiopatologia , Estimulação Encefálica Profunda/métodos , Feixe Prosencefálico Mediano/fisiologia , Filtro Sensorial/fisiologia , Idoso , Imagem de Tensor de Difusão , Feminino , Voluntários Saudáveis , Humanos , Masculino , Inibição Pré-Pulso/fisiologia , Cirurgia Assistida por ComputadorRESUMO
The human nucleus accumbens is thought to play an important role in guiding future action selection via an evaluation of current action outcomes. Here we provide electrophysiological evidence for a more direct, i.e., online, role during action preparation. We recorded local field potentials from the nucleus accumbens in patients with epilepsy undergoing surgery for deep brain stimulation. We found a consistent decrease in the power of alpha/beta oscillations (10-30 Hz) before and around the time of movements. This perimovement alpha/beta desynchronization was observed in seven of eight patients and was present both before instructed movements in a serial reaction time task as well as before self-paced, deliberate choices in a decision making task. A similar beta decrease over sensorimotor cortex and in the subthalamic nucleus has been directly related to movement preparation and execution. Our results support the idea of a direct role of the human nucleus accumbens in action preparation and execution.
Assuntos
Ritmo alfa/fisiologia , Ritmo beta/fisiologia , Atividade Motora/fisiologia , Núcleo Accumbens/fisiologia , Adulto , Comportamento de Escolha/fisiologia , Sincronização Cortical/fisiologia , Estimulação Encefálica Profunda , Epilepsia/diagnóstico por imagem , Epilepsia/fisiopatologia , Epilepsia/cirurgia , Epilepsia/terapia , Feminino , Dedos/fisiologia , Dedos/fisiopatologia , Lateralidade Funcional , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Movimento/fisiologia , Testes Neuropsicológicos , Núcleo Accumbens/diagnóstico por imagem , Núcleo Accumbens/fisiopatologia , Núcleo Accumbens/cirurgiaRESUMO
Hippocampal sclerosis in temporal lobe epilepsy (TLE) is often associated with hippocampal atrophy. This study assessed whether such atrophy is correlated with loss of gray matter volume in other brain regions. In 16 patients with TLE and clear magnetic resonance imaging-based evidence of hippocampal sclerosis, hippocampal volumes were determined manually and the local gray matter (LGM) amount was estimated throughout the entire brain using voxel-based morphometry. Voxelwise correlations between the volume of the sclerotic hippocampus and LGM were computed. The pattern of voxels whose LGM correlated with hippocampal volume outlined remarkably well the anatomy of the extended limbic system and included the parahippocampal region, cingulate gyrus throughout its extent, basal forebrain, thalamic nuclei, medial orbitofrontal areas and the insula. These correlations emerged mainly on the side ipsilateral to the affected hippocampus but were also found contralaterally. No such correlations were found in a group of 16 healthy controls. The present data show that hippocampal volume loss in TLE is associated with a widespread limbic systems atrophy. These findings are helpful to better understand the functional deficit and reorganization often found in temporal lobe epilepsy and will also provide a basis to assess neural plasticity in the limbic system for those patients who will undergo curative temporal lobe surgery.