The mirror neuron system under hypnosis - brain substrates of voluntary and involuntary motor activation in hypnotic paralysis.

INTRODUCTION: The neurobiological basis of non-organic movement impairments is still unknown. As conversion disorder and hypnotic states share many characteristics, we applied an experimental design established in conversion disorder to investigate hypnotic paralysis. METHODS: Movement imitation and observation were investigated by functional magnetic resonance imaging (fMRI) in 19 healthy subjects with and without hypnotically induced paralysis of their left hand. Paralysis-specific activation changes were explored in a multivariate model and functional interdependencies of brain regions by connectivity analysis. RESULTS: Hypnotic paralysis during movement imitation induced hypoactivation of the contralateral sensorimotor cortex (SMC) and ipsilateral cerebellum and increased activation of anterior cingulate cortex (ACC), frontal gyrus and insula. No paralysis-specific effects were revealed during movement observation. CONCLUSIONS: Hyperactivation of ACC, middle frontal gyrus (MFG), and insula might reflect attention (MFG), conflict-detection (ACC) and self-representation processes (insula) during hypnotic paralysis. The lack of effects in movement observation suggests that early motor processes are not disturbed due to the transient nature of the hypnotic impairment.

Volume estimation of the thalamus using freesurfer and stereology: consistency between methods.

Freely available automated MR image analysis techniques are being increasingly used to investigate neuroanatomical abnormalities in patients with neurological disorders. It is important to assess the specificity and validity of automated measurements of structure volumes with respect to reliable manual methods that rely on human anatomical expertise. The thalamus is widely investigated in many neurological and neuropsychiatric disorders using MRI, but thalamic volumes are notoriously difficult to quantify given the poor between-tissue contrast at the thalamic gray-white matter interface. In the present study we investigated the reliability of automatically determined thalamic volume measurements obtained using FreeSurfer software with respect to a manual stereological technique on 3D T1-weighted MR images obtained from a 3 T MR system. Further to demonstrating impressive consistency between stereological and FreeSurfer volume estimates of the thalamus in healthy subjects and neurological patients, we demonstrate that the extent of agreeability between stereology and FreeSurfer is equal to the agreeability between two human anatomists estimating thalamic volume using stereological methods. Using patients with juvenile myoclonic epilepsy as a model for thalamic atrophy, we also show that both automated and manual methods provide very similar ratios of thalamic volume loss in patients. This work promotes the use of FreeSurfer for reliable estimation of global volume in healthy and diseased thalami.

Microstructural and volumetric abnormalities of the putamen in juvenile myoclonic epilepsy.

PURPOSE: Patients with juvenile myoclonic epilepsy (JME) show evidence of microstructural white matter (WM) damage of thalamocortical fiber tracts and changes of blood oxygen level dependent (BOLD) signal in a striatothalamocortical network. The objective of the present study was to investigate microstructural and volumetric alterations of the putamen in patients with JME using diffusion tensor imaging (DTI) and conventional magnetic resonance imaging (MRI). METHODS: We performed DTI and MRI for 10 patients with JME and 59 age-matched neurologically healthy volunteers. Evaluation of microstructural damage was investigated using calculation of mean fractional anisotropy (FA) values in a priori regions of interest (ROIs) for the putamen, frontal lobe, and a thalamocortical region, after application of an improved eddy current correction method and a new statistical parametric mapping (SPM)-compatible toolbox incorporating intensive multicontrast FA image registration. Stereologic analysis on MRI was performed to estimate macroscopic volume of the putamen in both cerebral hemispheres for all subjects. KEY FINDINGS: Relative to controls, patients had significantly reduced FA in the frontal lobe (p = 0.01) and thalamocortical fiber WM (p < 0.001). In contrast, putamen FA was bilaterally increased (p = 0.01) and correlated with decreasing putamen volume (r(2) = -0.63, p = 0.004) in patients only. Putamen FA correlated negatively with onset of JME (total: r(2) = -0.50, p = 0.01), duration of JME (r(2) = 0.52, p = 0.01), and thalamocortical fiber FA (r(2) = -0.47, p = 0.01). SIGNIFICANCE: This is the first evidence of combined microstructural and macrostructural putamen abnormalities in patients with JME, with early age of onset and a longer duration of epilepsy being significant predictors for greater architectural alterations. These findings are consistent with studies indicating neurophysiologic abnormalities of frontostriatal networks in patients with JME, and may contribute to explain the frequent presentation of executive dysfunction in these patients. Confirmation and further exploration of the increase in putamen FA in patients with JME is required in larger samples.

Effect of gender on processing threat-related stimuli in patients with panic disorder: sex does matter.

BACKGROUND: Several studies have shown that female and male subjects process emotions differently. As women appear to be especially sensitive and responsive to negative and threatening stimuli, gender-specific emotional processing might be an important factor contributing to the increased likelihood of women compared to men to develop anxiety disorders, e.g. panic disorder (PD). METHODS: In this study, gender-specific neural activation during facial emotion processing was investigated in 20 PD patients (12 women, 8 men) by functional magnetic resonance imaging. RESULTS: Overall, significantly stronger activation, encompassing the amygdala, prefrontal, temporal, and occipital cortical areas, basal ganglia, and thalamus, was observed in women than in men during the processing of angry, fearful, or neutral but not happy facial expressions. Additionally, functional connectivity between the amygdala and prefrontal cortical areas and thalamus during the processing of angry facial expressions was significantly stronger in women than in men. CONCLUSIONS: These results emphasize gender as an important variable in neural activation patterns of emotional processing and may help to further elucidate the biological substrate of gender-specific susceptibility for PD.

Neural activation underlying acute grief in women after the loss of an unborn child.

OBJECTIVE: The traumatic loss of an unborn child by induced termination of pregnancy because of fetal malformation is a major life event that causes intense maternal grief. Increasing evidence supports the hypothesis that the same neural structures involved in the experience of physical pain are involved in the experience of social pain and loss. METHOD: To investigate neural activation patterns related to acute grief, the authors conducted a functional MRI study of 12 post-termination women and 12 noninduced women who delivered a healthy child. Brain activation was measured while participants viewed pictures of happy baby, happy adult, and neutral adult faces. RESULTS: Relative to comparison women, post-termination women showed greater activation in the middle and posterior cingulate gyrus, the inferior frontal gyrus, the middle temporal gyrus, the thalamus, and the brainstem in response to viewing happy baby faces. Functional connectivity between the cingulate gyrus and the thalamus during the processing of happy baby faces was significantly stronger in post-termination women. CONCLUSIONS: Overall, acute grief after the loss of an unborn child was closely related to the activation of the physical pain network encompassing the cingulate gyrus, the inferior frontal gyrus, the thalamus, and the brainstem. To the authors' knowledge, the stronger functional thalamocingulate connectivity in post-termination women is the first in vivo demonstration of an involvement of the neural maternal attachment network in grief after the loss of an unborn child.

fMRI studies of sensitivity and habituation effects within the auditory cortex at 1.5 T and 3 T.

PURPOSE: To assess habituation effects in relation to field strength by fMRI at 1.5 vs. 3.0 T within the auditory cortex of healthy subjects. MATERIALS AND METHODS: fMRI experiments were performed on 19 healthy subjects at 1.5 T (N = 12) and 3 T (N = 12). The auditory cortex was stimulated binaurally by digitally generated pulsed (nu = 5 Hz) 800 Hz sine tones with three alternating on and off periods. RESULTS: The mean activation after stimulation (4.4% +/- 1.2% (1.5 T) and 5.3% +/- 2.3% (3 T)) and number of activated pixels (96.7 +/- 49.8 (1.5 T) and 139.9 +/- 101 (3 T)) were higher at 3 T compared to 1.5 T; however, that difference did not reach statistical significance. A characteristic signal decay with repeated stimuli was revealed at both 1.5 and 3 T, and the response to the second and third stimulation blocks was significantly lower compared to the first. The habituation pattern was the same, independently of field strength and age. CONCLUSION: The mean activation and number of pixels were only modestly higher at 3 T, probably due to higher physiologic noise and higher local macroscopic susceptibility gradients within the temporal lobes at 3 T. Our data reveal that measured auditory habituation is independent of field strength, and data obtained at two different field strengths do not differ fundamentally in this context.

Nonlinear responses within the medial prefrontal cortex reveal when specific implicit information influences economic decision making.

BACKGROUND AND PURPOSE: The authors used functional magnetic resonance imaging (fMRI) to investigate how individual economic decisions are influenced by implicit memory contributions. METHODS: Twenty-two participants were asked to make binary decisions between different brands of sensorily nearly undistinguishable consumer goods. Changes of brain activity comparing decisions in the presence or absence of a specific target brand were detected by fMRI. RESULTS: Only when the tar get brand was the participant's favorite one did the authors find reduced activation in the dorsolateral prefrontal, posterior parietal, and occipital cortices and the left premotor area (Brodmann areas [BA] 9, 46, 7/19, and 6). Simultaneously, activity was increased in the inferior precuneus and posterior cingulate (BA 7), right superior frontal gyrus (BA 10), right supramarginal gyrus (BA 40), and, most pronounced, in the ventromedial prefrontal cortex (BA 10). CONCLUSIONS: For products mainly distinguishable by brand information, the authors revealed a nonlinear winner-take-all effect for a participant's favorite brand characterized, on one hand, by reduced activation in brain areas associated with working memory and reasoning and, on the other hand, increased activation in areas involved in processing of emotions and self-reflections during decision making.