Amir Samii

Changes of resting state brain networks in amyotrophic lateral sclerosis.

The defining feature of amyotrophic lateral sclerosis is degeneration of upper and lower motor neurons but extramotor involvement, evidenced for example by executive dysfunction, has also been demonstrated. Here we employed a novel functional imaging approach, the analysis of resting state activity, followed by the definition of functionally connected brain networks by independent component analysis (ICA) to assess differences between ALS patients (n=20) and healthy controls (n=20). ICA analysis revealed 5 typical brain networks among which the so-called default mode network and the sensori-motor network showed distinct differences between patients and controls. The default mode network showed less activation in patients in several regions including the ventral anterior cingulate cortex, posterior cingulate cortex and the left and right inferior parietal cortex, regions that have been linked previously to executive functions. The sensori-motor network showed group differences in the premotor cortex. We propose that resting state analysis affords a new and simple means to assess disease-related neurofunctional alterations in widespread brain networks. A decisive advantage is that no task is demanded from the subjects and, thus, the problem of differential task difficulty and effort between groups is circumvented.

Functional neuroimaging at different disease stages reveals distinct phases of neuroplastic changes in amyotrophic lateral sclerosis.

Some previous functional magnetic resonance imaging (fMRI) studies have revealed increased activation in amyotrophic lateral sclerosis (ALS) patients but longitudinal data on such activation changes are lacking. To assess the time course of changes in fMRI patterns and their potential contribution to the understanding of ALS pathophysiology, we, therefore, investigated a total of 22 patients with ALS and matched control participants while they performed a blocked motor task. Patients were assigned to three groups according to whether they had no (MRC grade 5), mild (MRC 4), or marked (MRC 3) weakness of the examined right hand. Significant activations were seen in primary motor and premotor cortex, somatosensory cortex, supplementary motor area and subcortical areas in all groups. The size of the activated area in the contralateral sensorimotor cortex was increased to a similar degree in all three ALS groups compared to control participants irrespective of weakness on clinical examination. Whereas movement related signal change and beta weights extracted from the activated cluster were unchanged relative to controls in ALS patients with no weakness, a marked decrease of these parameters was seen in patients with weakness. Two distinct stages of neuroplastic changes could be identified in ALS (first: increase of the activated area in contralateral sensorimotor cortex; second: reduction of signal change and beta weights with increasing weakness). We interpret the increase of the activated area as a result of decreased intracortical inhibition and the reduction of movement related signal change and beta weights as a consequence of loss of upper motor neurons. Hum Brain Mapp, 2011.

Brain activations reflect individual discount rates in intertemporal choice

Humans discount the value of future rewards following a hyperbolic function and thus may prefer a smaller immediate reward over a larger delayed reward. Marked interindividual differences in the steepness of this discounting function can be observed which can be quantified by the parameter k of the discount function. Here, we asked how differences in delay discounting behaviour are reflected by brain activation patterns. Sixteen healthy participants were studied in a slow event-related functional magnetic resonance imaging experiment at 3T. In each trial, participants had to decide between a smaller but immediately available monetary reward (ranging between 14 and 84 Euro) and a larger delayed reward (26 to 89 Euro; delay 5 to 169days) by button press. Participants had the chance to receive the reward corresponding to one of their decisions at the end of the experiment. As expected, participants differed widely with respect to the steepness of their discount function. By contrasting decisions at or near the individual participants indifference point (as determined by parameter k) with trials either well below or well above this point two different brain networks with opposing activation patterns were revealed: Trials below or above the indifference point were associated with activation in the ventral striatum and ventromedial prefrontal cortex, whereas decisions at the indifference point gave rise to activation in medial prefrontal cortex. The opposite effects in the two systems at individual indifference point were interpreted as a reflection of response conflict.

Changes in Resting-State Brain Networks in Writer's Cramp

Writers cramp (WC) is characterized by excessive cocontractions of agonist and antagonist hand and forearm muscles during writing. Changes in functional magnetic resonance imaging activation patterns in such conditions can be ambiguous as they might either reflect some aspect of the primary pathophysiological mechanism or, alternatively, may be the result of adaptive actions during task execution. To circumvent this problem, we examined WC patients during rest, i.e., without a task, using independent component analysis (ICA) applied to the blood oxygen level‐dependent time series.

Observation of sonified movements engages a basal ganglia frontocortical network.

BackgroundProducing sounds by a musical instrument can lead to audiomotor coupling, i.e. the joint activation of the auditory and motor system, even when only one modality is probed. The sonification of otherwise mute movements by sounds based on kinematic parameters of the movement has been shown to improve motor performance and perception of movements.ResultsHere we demonstrate in a group of healthy young non-athletes that congruently (sounds match visual movement kinematics) vs. incongruently (no match) sonified breaststroke movements of a human avatar lead to better perceptual judgement of small differences in movement velocity. Moreover, functional magnetic resonance imaging revealed enhanced activity in superior and medial posterior temporal regions including the superior temporal sulcus, known as an important multisensory integration site, as well as the insula bilaterally and the precentral gyrus on the right side. Functional connectivity analysis revealed pronounced connectivity of the STS with the basal ganglia and thalamus as well as frontal motor regions for the congruent stimuli. This was not seen to the same extent for the incongruent stimuli.ConclusionsWe conclude that sonification of movements amplifies the activity of the human action observation system including subcortical structures of the motor loop. Sonification may thus be an important method to enhance training and therapy effects in sports science and neurological rehabilitation.

Structural neuroplasticity in expert pianists depends on the age of musical training onset

In the last decade, several studies have investigated the neuroplastic changes induced by long-term musical training. Here we investigated structural brain differences in expert pianists compared to non-musician controls, as well as the effect of the age of onset (AoO) of piano playing. Differences with non-musicians and the effect of sensitive periods in musicians have been studied previously, but importantly, this is the first time in which the age of onset of music-training was assessed in a group of musicians playing the same instrument, while controlling for the amount of practice. We recruited a homogeneous group of expert pianists who differed in their AoO but not in their lifetime or present amount of training, and compared them to an age-matched group of non-musicians. A subset of the pianists also completed a scale-playing task in order to control for performance skill level differences. Voxel-based morphometry analysis was used to examine gray-matter differences at the whole-brain level. Pianists showed greater gray matter (GM) volume in bilateral putamen (extending also to hippocampus and amygdala), right thalamus, bilateral lingual gyri and left superior temporal gyrus, but a GM volume shrinkage in the right supramarginal, right superior temporal and right postcentral gyri, when compared to non-musician controls. These results reveal a complex pattern of plastic effects due to sustained musical training: a network involved in reinforcement learning showed increased GM volume, while areas related to sensorimotor control, auditory processing and score-reading presented a reduction in the volume of GM. Behaviorally, early-onset pianists showed higher temporal precision in their piano performance than late-onset pianists, especially in the left hand. Furthermore, early onset of piano playing was associated with smaller GM volume in the right putamen and better piano performance (mainly in the left hand). Our results, therefore, reveal for the first time in a single large dataset of healthy pianists the link between onset of musical practice, behavioral performance, and putaminal gray matter structure. In summary, skill-related plastic adaptations may include decreases and increases in GM volume, dependent on an optimization of the system caused by an early start of musical training. We believe our findings enrich the plasticity discourse and shed light on the neural basis of expert skill acquisition.

Patterns of cortical activity differ in ALS patients with limb and/or bulbar involvement depending on motor tasks.

Functional magnetic resonance imaging (fMRI) of hand movements in amyotrophic lateral sclerosis (ALS) has repeatedly demonstrated increased activation in cortical and subcortical areas, whereas a single study has suggested decreased rather than increased activations for tongue movements in patients with bulbar involvement. This points to differences in the pathophysiology and may correspond to the different time-course of disease for patients with and without bulbar involvement. We, therefore, compared the cortical activity during movements of the tongue and right hand using fMRI to delineate the neurofunctional correlates of bulbar versus limb symptoms in 20 ALS patients (11 with bulbar signs) and age-matched controls. During vertical tongue movements, the cortical activation pattern in ALS patients without bulbar signs did not differ from the control group. However, presence of bulbar signs caused a significant decrease of cortical activation. An increased cortical activity during the hand movement in all ALS patients was evident, regardless of site of onset and presence of bulbar signs. Thus, two different patterns of cortical activation changes suggesting fundamental differences in the neurodegenerative process and subsequent reorganisation processes exist for limb and bulbar movements.

Play it again, Sam: brain correlates of emotional music recognition

Background: Music can elicit strong emotions and can be remembered in connection with these emotions even decades later. Yet, the brain correlates of episodic memory for highly emotional music compared with less emotional music have not been examined. We therefore used fMRI to investigate brain structures activated by emotional processing of short excerpts of film music successfully retrieved from episodic long-term memory. Methods: Eighteen non-musicians volunteers were exposed to 60 structurally similar pieces of film music of 10 s length with high arousal ratings and either less positive or very positive valence ratings. Two similar sets of 30 pieces were created. Each of these was presented to half of the participants during the encoding session outside of the scanner, while all stimuli were used during the second recognition session inside the MRI-scanner. During fMRI each stimulation period (10 s) was followed by a 20 s resting period during which participants pressed either the “old” or the “new” button to indicate whether they had heard the piece before. Results: Musical stimuli vs. silence activated the bilateral superior temporal gyrus, right insula, right middle frontal gyrus, bilateral medial frontal gyrus and the left anterior cerebellum. Old pieces led to activation in the left medial dorsal thalamus and left midbrain compared to new pieces. For recognized vs. not recognized old pieces a focused activation in the right inferior frontal gyrus and the left cerebellum was found. Positive pieces activated the left medial frontal gyrus, the left precuneus, the right superior frontal gyrus, the left posterior cingulate, the bilateral middle temporal gyrus, and the left thalamus compared to less positive pieces. Conclusion: Specific brain networks related to memory retrieval and emotional processing of symphonic film music were identified. The results imply that the valence of a music piece is important for memory performance and is recognized very fast.

Excessive users of violent video games do not show emotional desensitization: an fMRI study.

Playing violent video games have been linked to long-term emotional desensitization. We hypothesized that desensitization effects in excessive users of violent video games should lead to decreased brain activations to highly salient emotional pictures in emotional sensitivity brain regions. Twenty-eight male adult subjects showing excessive long-term use of violent video games and age and education matched control participants were examined in two experiments using standardized emotional pictures of positive, negative and neutral valence. No group differences were revealed even at reduced statistical thresholds which speaks against desensitization of emotion sensitive brain regions as a result of excessive use of violent video games.

Amyotrophic lateral sclerosis affects cortical and subcortical activity underlying motor inhibition and action monitoring.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by muscular atrophy, spasticity, and bulbar signs caused by loss of upper and lower motor neurons. Evidence suggests that ALS additionally affects other brain areas including premotor cortex and supplementary motor area. Here, we studied movement execution and inhibition in ALS patients using a stop‐signal paradigm and functional magnetic resonance imaging. Seventeen ALS patients and 17 age‐matched healthy controls performed a stop‐signal task that required responding with a button press to a right‐ or left‐pointing black arrow (go‐stimuli). In stop‐trials, a red arrow (stop‐stimulus) was presented shortly after the black arrow indicating to withhold the prepared movement. Patients had by trend higher reaction times in go‐trials but did not differ significantly in their inhibition performance. Patients showed stronger inhibition‐related activity in inferior, superior, and middle frontal gyri as well as in putamen and pallidum. Error‐related activity, conversely, was found to be stronger in healthy controls, particularly in the insula bilaterally. Patients also showed increased activity in the motor cortex during button presses. The results provide evidence for altered prefrontal and subcortical networks underlying motor execution, motor inhibition, and error monitoring in ALS. Hum Brain Mapp 36:2878–2889, 2015.