Two action systems in the human brain

The distinction between dorsal and ventral visual processing streams, first proposed by Ungerleider and Mishkin (1982) and later refined by Milner and Goodale (1995) has been elaborated substantially in recent years, spurred by two developments. The first was proposed in large part by Rizzolatti and Matelli (2003) and is a more detailed description of the multiple neural circuits connecting the frontal, temporal, and parietal cortices. Secondly, there are a number of behavioral observations that the classic "two visual systems" hypothesis is unable to accommodate without additional assumptions. The notion that the Dorsal stream is specialized for "where" or "how" actions and the Ventral stream for "What" knowledge cannot account for two prominent disorders of action, limb apraxia and optic ataxia, that represent a double dissociation in terms of the types of actions that are preserved and impaired. A growing body of evidence, instead, suggests that there are at least two distinct Dorsal routes in the human brain, referred to as the "Grasp" and "Use" systems. Both of these may be differentiated from the Ventral route in terms of neuroanatomic localization, representational specificity, and time course of information processing.

Slow wave sleep induced by GABA agonist tiagabine fails to benefit memory consolidation

STUDY OBJECTIVES

Slow wave sleep (SWS) plays a pivotal role in consolidating memories. Tiagabine has been shown to increase SWS in favor of REM sleep without impacting subjective sleep. However, it is unknown whether this effect is paralleled by an improved sleep-dependent consolidation of memory.

DESIGN

This double-blind within-subject crossover study tested sensitivity of overnight retention of declarative neutral and emotional materials (word pairs, pictures) as well as a procedural memory task (sequence finger tapping) to oral administration of placebo or 10 mg tiagabine (at 22:30).

PARTICIPANTS

Fourteen healthy young men aged 21.9 years (range 18-28 years).

MEASUREMENTS AND RESULTS

Tiagabine significantly increased the time spent in SWS and decreased REM sleep compared to placebo. Tiagabine also enhanced slow wave activity (0.5-4.0 Hz) and density of < 1 Hz slow oscillations during NREM sleep. Fast (12-15 Hz) and slow (9-12 Hz) spindle activity, in particular that occurring phase-locked to the slow oscillation cycle, was decreased following tiagabine. Despite signs of deeper and more SWS, overnight retention of memory tested after sleep the next evening (19:30) was generally not improved after tiagabine, but on average even lower than after placebo, with this impairing effect reaching significance for procedural sequence finger tapping.

CONCLUSIONS

Our data show that increasing slow wave sleep with tiagabine does not improve memory consolidation. Possibly this is due to functional differences from normal slow wave sleep, i.e., the concurrent suppressive influence of tiagabine on phase-locked spindle activity.

Combined space and alertness related therapy of visual hemineglect: effect of therapy frequency

The combined efficacy of space- and alertness related training in chronic hemineglect was tested behaviorally and in a longitudinal fMRI study. Earlier results had shown that both space as well as alertness related training as single intervention methods lead to short term improvement which, however, is not stable for longer time periods. The neurobiological data obtained in these studies revealed differential cortical reorganization patterns for the two training approaches thereby leading to the hypothesis that a combination of both trainings might result in stronger and longer lasting effects. The results of our current study, however, - at least at first glance - do not clearly corroborate this hypothesis, because neither alertness training alone nor the combination with OKS on the group level led to significant behavioral improvement, although four of the six patients after alertness and even more after combined training showed a higher percentage of behavioral improvement than during baseline. Despite the lack of clearcut behavioral training induced improvement we found right parietal or fronto-parietal increase of activation in the imaging data immediately after combined training and at follow-up 3 weeks later. The study design had called for splitting up training time between the two training approaches in order to match total training time with our earlier single training studies. The results of our current study are discussed as a possible consequence of reduced training time and intensity of both training measures under the combined training situation.

Differential role of the Mentalizing and the Mirror Neuron system in the imitation of communicative gestures

Successful social interaction requires recognising the intention of another person's communicative gestures. At a neural level, this process may involve neural activity in different systems, such as the mentalizing system (MS) and the mirror neuron system (MNS). The aim of the present study was to explore the neural correlates of communicative gestures during observation and execution of these gestures. Twenty participants watched video clips of an actor executing social gestures (S), non-social gestures (NS) and meaningless gestures (ML). During fMRI data acquisition, participants were asked to observe (O) and subsequently to execute (E) one of two tasks: imitate the gesture presented (IMI) or perform a motor control task (CT). For the contrast IMI>CT we found activations in the core areas of the MNS [inferior parietal lobule (IPL) and inferior frontal cortex, the posterior part of pars opercularis], as well as in areas related to the MS [superior temporal sulcus (STS) and middle cingulate cortex]. For S>NS, we found activations in the left medial orbitofrontal cortex (mOFC), right superior frontal cortex and middle cingulate cortex. The interaction of stimulus condition (S vs NS) and task (IMI vs CT) revealed activation in the right IPL. For the interaction between observation vs execution (O vs E), task (IMI vs CT) and stimulus condition (S vs NS) we found activation in the right mOFC. Our data suggest that imitation is differentially processed in the MNS as well as in the MS. The activation in IPL is enhanced during the processing of social gestures most likely due to their communicative intention. The activation of IPL together with medial frontal areas may contribute to mentalizing processes. The interaction in the mOFC suggests an involvement of self-referential processes in the processing of social gesture.

Are abstract action words embodied? An fMRI investigation at the interface between language and motor cognition

The cognitive and neural representation of abstract words is still an open question for theories of embodied cognition. Generally, it is proposed that abstract words are grounded in the activation of sensorimotor or at least experiential properties, exactly as concrete words. Further behavioral theories propose multiple representations evoked by abstract and concrete words. We conducted a functional magnetic resonance imaging (fMRI) study to investigate the neural correlates of concrete and abstract multi-word expressions in an action context. Participants were required to read simple sentences which combined each concrete noun with an adequate concrete verb and an adequate abstract verb, as well as an adequate abstract noun with either kind of verbs previously used. Thus, our experimental design included a continuum from pure concreteness to mere abstractness. As expected, comprehension of both concrete and abstract language content activated the core areas of the sensorimotor neural network namely the left lateral (precentral gyrus) and medial (supplementary motor area) premotor cortex. While the purely concrete multi-word expressions elicited activations within the left inferior frontal gyrus (pars triangularis) and two foci within the left inferior parietal cortex, the purely abstract multi-word expressions were represented in the anterior part of left middle temporal gyrus that is part of the language processing system. Although the sensorimotor neural network is engaged in both concrete and abstract language contents, the present findings show that concrete multi-word processing relies more on the sensorimotor system, and abstract multi-word processing relies more on the linguistic system.

Neural correlates of impaired emotion processing in manifest Huntington's disease

The complex phenotype of Huntington's disease (HD) encompasses motor, psychiatric and cognitive dysfunctions, including early impairments in emotion recognition. In this first functional magnetic resonance imaging study, we investigated emotion-processing deficits in 14 manifest HD patients and matched controls. An emotion recognition task comprised short video clips displaying one of six basic facial expressions (sadness, happiness, disgust, fear, anger and neutral). Structural changes between patients and controls were assessed by means of voxel-based morphometry. Along with deficient recognition of negative emotions, patients exhibited predominantly lower neural response to stimuli of negative valences in the amygdala, hippocampus, striatum, insula, cingulate and prefrontal cortices, as well as in sensorimotor, temporal and visual areas. Most of the observed reduced activity patterns could not be explained merely by regional volume loss. Reduced activity in the thalamus during fear correlated with lower thalamic volumes. During the processing of sadness, patients exhibited enhanced amygdala and hippocampal activity along with reduced recruitment of the medial prefrontal cortex. Higher amygdala activity was related to more pronounced amygdala atrophy and disease burden. Overall, the observed emotion-related dysfunctions in the context of structural neurodegeneration suggest both disruptions of striatal-thalamo-cortical loops and potential compensation mechanism with greater disease severity in manifest HD.

The Role of Human Parietal Area 7A as a Link between Sequencing in Hand Actions and in Overt Speech Production

Research on the evolutionary basis of the human language faculty has proposed the mirror neuron system as a link between motor processing and speech development. Consequently, most work has focused on the left inferior frontal cortex, in particular Broca's region, and the left inferior parietal cortex. However, the direct link between planning of hand motor and speech actions has yet to be elucidated. Thus, the present study investigated whether motor sequencing of hand vs. speech actions has a common neural denominator. For the hand motor task, 25 subjects performed single, repeated, or sequenced button presses with either the left or right hand. The speech task was in analogy; the same subjects produced the syllable "po" once or repeatedly, or a sequence of different syllables ("po-pi-po"). Speech motor vs. hand motor effectors resulted in increased perisylvian activation including Broca's region (left area 44 and areas medially adjacent to left area 45). In contrast, common activation for sequenced vs. repeated production of button presses and syllables revealed the effector-independent involvement of left area 7A in the superior parietal lobule (SPL) in sequencing. These data demonstrate that sequencing of vocal gestures, an important precondition for ordered utterances and ultimately human speech, shares area 7A, rather than inferior parietal regions, as a common cortical module with hand motor sequencing. Interestingly, area 7A has previously also been shown to be involved in the observation of hand and non-hand actions. In combination with the literature, the present data thus suggest a distinction between area 44, which is specifically recruited for (cognitive aspects of) speech, and SPL area 7A for general aspects of motor sequencing. In sum, the study demonstrates a previously underspecified role of the SPL in the origins of speech, and may be discussed in the light of embodiment of speech and language in the motor system.

Abstract and concrete phrases processing differentially modulates cortico-spinal excitability

An important challenge of embodied theories is to explain the comprehension of abstract sentences. The aim of the present study was to scrutinize the role of the motor cortex in this process. We developed a new paradigm to study the abstract-concrete dimension by combining concrete (i.e., action-related) and abstract (i.e., non-action-related) verbs with nouns of graspable and non-graspable objects. Using these verb-noun combinations we performed a Transcranial Magnetic Stimulation (TMS) on the left primary motor cortex while participants performed a sentence sensibility task. Single-TMS pulses were delivered 250ms after verb or noun presentation in each of four combinations of abstract and concrete verbs and nouns. To evaluate cortico-spinal excitability we registered the electromyographic activity of the right first dorsal interosseous muscle. As to verb-noun integration, analysis of motor evoked potentials (MEPs) after TMS pulse during noun presentation revealed greater peak-to-peak amplitude in phrases containing abstract rather than concrete verbs. Response times were also collected and showed that compatible (Concrete-Concrete and Abstract-Abstract) combinations were processed faster than mixed ones; moreover in combinations containing concrete verbs, participants were faster when the pulse was delivered on the first word (verb) than on the second one (noun). Results support previous findings showing early activation of hand-related areas after concrete verbs processing. The prolonged or delayed activation of the same areas by abstract verbs will be discussed in the framework of recent embodied theories based on multiple types of representation, particularly theories emphasizing the role of different acquisition mechanisms for concrete and abstract words (Borghi and Cimatti, 2009,2012).

Observation and execution of upper-limb movements as a tool for rehabilitation of motor deficits in paretic stroke patients: protocol of a randomized clinical trial

Background

Evidence exist that motor observation activates the same cortical motor areas that are involved in the performance of the observed actions. The so called “mirror neuron system” has been proposed to be responsible for this phenomenon. We employ this neural system and its capability to re-enact stored motor representations as a tool for rehabilitating motor control. In our new neurorehabilitative schema (videotherapy) we combine observation of daily actions with concomitant physical training of the observed actions focusing on the upper limbs. Following a pilot study in chronic patients in an ambulatory setting, we currently designed a new multicenter clinical study dedicated to patients in the sub-acute state after stroke using a home-based self-induced training. Within our protocol we assess 1) the capability of action observation to elicit rehabilitational effects in the motor system, and 2) the capacity of this schema to be performed by patients without assistance from a physiotherapist. The results of this study would be of high health and economical relevance.

Methods/design

A controlled, randomized, multicenter, paralleled, 6 month follow-up study will be conducted on three groups of patients: one group will be given the experimental treatment whereas the other two will participate in control treatments. All patients will undergo their usual rehabilitative treatment beside participation in the study. The experimental condition consists in the observation and immediate imitation of common daily hand and arm actions. The two parallel control groups are a placebo group and a group receiving usual rehabilitation without any trial-related treatment. Trial randomization is provided via external data management. The primary efficacy endpoint is the improvement of the experimental group in a standardized motor function test (Wolf Motor Function Test) relative to control groups. Further assessments refer to subjective and qualitative rehabilitational scores. This study has been reviewed and approved by the ethics committee of Aachen University.

Discussion

This therapy provides an extension of therapeutic procedures for recovery after stroke and emphasizes the importance of action perception in neurorehabilitation The results of the study could become implemented into the wide physiotherapeutic practice, for example as an ad on and individualized therapy.

Altered velocity processing in schizophrenia during pursuit eye tracking

Smooth pursuit eye movements (SPEM) are needed to keep the retinal image of slowly moving objects within the fovea. Depending on the task, about 50%-80% of patients with schizophrenia have difficulties in maintaining SPEM. We designed a study that comprised different target velocities as well as testing for internal (extraretinal) guidance of SPEM in the absence of a visual target. We applied event-related fMRI by presenting four velocities (5, 10, 15, 20°/s) both with and without intervals of target blanking. 17 patients and 16 healthy participants were included. Eye movements were registered during scanning sessions. Statistical analysis included mixed ANOVAs and regression analyses of the target velocity on the Blood Oxygen Level Dependency (BOLD) signal. The main effect group and the interaction of velocity×group revealed reduced activation in V5 and putamen but increased activation of cerebellar regions in patients. Regression analysis showed that activation in supplementary eye field, putamen, and cerebellum was not correlated to target velocity in patients in contrast to controls. Furthermore, activation in V5 and in intraparietal sulcus (putative LIP) bilaterally was less strongly correlated to target velocity in patients than controls. Altered correlation of target velocity and neural activation in the cortical network supporting SPEM (V5, SEF, LIP, putamen) implies impaired transformation of the visual motion signal into an adequate motor command in patients. Cerebellar regions seem to be involved in compensatory mechanisms although cerebellar activity in patients was not related to target velocity.

Investigating function and connectivity of morphometric findings--exemplified on cerebellar atrophy in spinocerebellar ataxia 17 (SCA17)

Spinocerebellar ataxia type 17 (SCA17) is a rare autosomal dominant neurodegenerative disorder characterized by progressive cerebellar ataxia but also a broad spectrum of other neuropsychiatric signs. As anatomical and structural studies have shown severe cerebellar atrophy in SCA17 and a differentiation of the human cerebellum into an anterior sensorimotor and posterior cognitive/emotional partition has been implicated, we aimed at investigating functional connectivity patterns of two cerebellar clusters of atrophy revealed by a morphometric analysis in SCA17 patients. In particular, voxel-based morphometry (VBM) revealed a large cluster of atrophy in SCA17 in the bilateral anterior cerebellum (lobule V) and another one in the left posterior cerebellum (lobules IX, VIIb, VIIIA, VIIIB). These two cerebellar clusters were used as seeds for functional connectivity analyses using task-based meta-analytic connectivity modeling (MACM) and task-free resting state connectivity analysis. Results demonstrated first consistent functional connectivity throughout the cerebellum itself; the anterior cerebellar seed showed stronger connectivity to lobules V, VI and to some extent I-IV, and the posterior cerebellar seed to the posterior lobules VI-IX. Importantly, the cerebellar anterior seed also showed consistently stronger functional connectivity than the posterior one with pre- and motor areas as well as the primary somatosensory cortex. In turn, task-based task-independent functional connectivity analyses revealed that the cerebellar posterior seed was linked with fronto-temporo-parietal areas as well as partly the insula and the thalamus, i.e., brain regions implicated in cognitive and affective processes. Functional characterization of experiments activating either cerebellar seed further corroborated this notion, revealing mainly motor-related functions for the anterior cluster and predominantly cognitive functions were associated for the posterior one. The differential functional connectivity of the cerebellar anterior and posterior cluster highlights the manifold connections and dichotomy of the human cerebellum, providing additional valuable information about probably disrupted cerebellar-cerebral connections and reflecting the brunt of motor but also the broad spectrum of neuropsychiatric deficits in SCA17.

The time course of neurolinguistic and neuropsychological symptoms in three cases of logopenic primary progressive aphasia

Primary progressive aphasia (PPA) is a rare clinical dementia syndrome affecting predominantly language abilities. Word-finding difficulties and comprehension deficits despite relatively preserved cognitive functions are characteristic symptoms during the first two years, and distinguish PPA from other dementia types like Alzheimer's disease. However, the dynamics of changes in language and non-linguistic abilities are not well understood. Most studies on progression used cross-sectional designs, which provide only limited insight into the course of the disease. Here we report the results of a longitudinal study in three cases of logopenic PPA over a period of 18 months, with exemplary longitudinal data from one patient even over 46 months. A comprehensive battery of neurolinguistic and neuropsychological tests was applied four times at intervals of six months. Over this period, deterioration of verbal abilities such as picture naming, story retelling, and semantic word recall was found, and the individual decline was quantified and compared between the three patients. Furthermore, decrease in non-verbal skills such as divided attention and increasing apraxia was observed in all three patients. In addition, inter-subject variability in the progression with different focuses was observed, with one patient developing a non-fluent PPA variant. The longitudinal, multivariate investigation of logopenic PPA thus provides novel insights into the progressive deterioration of verbal as well as non-verbal abilities. These deficits may further interact and thus form a multi-causal basis for the patients' problems in every-day life which need to be considered when planning individually targeted intervention in PPA.

Compensatory premotor activity during affective face processing in subclinical carriers of a single mutant Parkin allele

Patients with Parkinson's disease suffer from significant motor impairments and accompanying cognitive and affective dysfunction due to progressive disturbances of basal ganglia–cortical gating loops. Parkinson's disease has a long presymptomatic stage, which indicates a substantial capacity of the human brain to compensate for dopaminergic nerve degeneration before clinical manifestation of the disease. Neuroimaging studies provide evidence that increased motor-related cortical activity can compensate for progressive dopaminergic nerve degeneration in carriers of a single mutant Parkin or PINK1 gene, who show a mild but significant reduction of dopamine metabolism in the basal ganglia in the complete absence of clinical motor signs. However, it is currently unknown whether similar compensatory mechanisms are effective in non-motor basal ganglia–cortical gating loops. Here, we ask whether asymptomatic Parkin mutation carriers show altered patterns of brain activity during processing of facial gestures, and whether this might compensate for latent facial emotion recognition deficits. Current theories in social neuroscience assume that execution and perception of facial gestures are linked by a special class of visuomotor neurons (‘mirror neurons’) in the ventrolateral premotor cortex/pars opercularis of the inferior frontal gyrus (Brodmann area 44/6). We hypothesized that asymptomatic Parkin mutation carriers would show increased activity in this area during processing of affective facial gestures, replicating the compensatory motor effects that have previously been observed in these individuals. Additionally, Parkin mutation carriers might show altered activity in other basal ganglia–cortical gating loops. Eight asymptomatic heterozygous Parkin mutation carriers and eight matched controls underwent functional magnetic resonance imaging and a subsequent facial emotion recognition task. As predicted, Parkin mutation carriers showed significantly stronger activity in the right ventrolateral premotor cortex during execution and perception of affective facial gestures than healthy controls. Furthermore, Parkin mutation carriers showed a slightly reduced ability to recognize facial emotions that was least severe in individuals who showed the strongest increase of ventrolateral premotor activity. In addition, Parkin mutation carriers showed a significantly weaker than normal increase of activity in the left lateral orbitofrontal cortex (inferior frontal gyrus pars orbitalis, Brodmann area 47), which was unrelated to facial emotion recognition ability. These findings are consistent with the hypothesis that compensatory activity in the ventrolateral premotor cortex during processing of affective facial gestures can reduce impairments in facial emotion recognition in subclinical Parkin mutation carriers. A breakdown of this compensatory mechanism might lead to the impairment of facial expressivity and facial emotion recognition observed in manifest Parkinson's disease.

Brain energy consumption induced by electrical stimulation promotes systemic glucose uptake

BACKGROUND

Controlled transcranial stimulation of the brain is part of clinical treatment strategies in neuropsychiatric diseases such as depression, stroke, or Parkinson's disease. Manipulating brain activity by transcranial stimulation, however, inevitably influences other control centers of various neuronal and neurohormonal feedback loops and therefore may concomitantly affect systemic metabolic regulation. Because hypothalamic adenosine triphosphate-sensitive potassium channels, which function as local energy sensors, are centrally involved in the regulation of glucose homeostasis, we tested whether transcranial direct current stimulation (tDCS) causes an excitation-induced transient neuronal energy depletion and thus influences systemic glucose homeostasis and related neuroendocrine mediators.

METHODS

In a crossover design testing 15 healthy male volunteers, we increased neuronal excitation by anodal tDCS versus sham and examined cerebral energy consumption with ³¹phosphorus magnetic resonance spectroscopy. Systemic glucose uptake was determined by euglycemic-hyperinsulinemic glucose clamp, and neurohormonal measurements comprised the parameters of the stress systems.

RESULTS

We found that anodic tDCS-induced neuronal excitation causes an energetic depletion, as quantified by ³¹phosphorus magnetic resonance spectroscopy. Moreover, tDCS-induced cerebral energy consumption promotes systemic glucose tolerance in a standardized euglycemic-hyperinsulinemic glucose clamp procedure and reduces neurohormonal stress axes activity.

CONCLUSIONS

Our data demonstrate that transcranial brain stimulation not only evokes alterations in local neuronal processes but also clearly influences downstream metabolic systems regulated by the brain. The beneficial effects of tDCS on metabolic features may thus qualify brain stimulation as a promising nonpharmacologic therapy option for drug-induced or comorbid metabolic disturbances in various neuropsychiatric diseases.

Abstract and concrete sentences, embodiment, and languages

One of the main challenges of embodied theories is accounting for meanings of abstract words. The most common explanation is that abstract words, like concrete ones, are grounded in perception and action systems. According to other explanations, abstract words, differently from concrete ones, would activate situations and introspection; alternatively, they would be represented through metaphoric mapping. However, evidence provided so far pertains to specific domains. To be able to account for abstract words in their variety we argue it is necessary to take into account not only the fact that language is grounded in the sensorimotor system, but also that language represents a linguistic-social experience. To study abstractness as a continuum we combined a concrete (C) verb with both a concrete and an abstract (A) noun; and an abstract verb with the same nouns previously used (grasp vs. describe a flower vs. a concept). To disambiguate between the semantic meaning and the grammatical class of the words, we focused on two syntactically different languages: German and Italian. Compatible combinations (CC, AA) were processed faster than mixed ones (CA, AC). This is in line with the idea that abstract and concrete words are processed preferentially in parallel systems - abstract in the language system and concrete more in the motor system, thus costs of processing within one system are the lowest. This parallel processing takes place most probably within different anatomically predefined routes. With mixed combinations, when the concrete word preceded the abstract one (CA), participants were faster, regardless of the grammatical class and the spoken language. This is probably due to the peculiar mode of acquisition of abstract words, as they are acquired more linguistically than perceptually. Results confirm embodied theories which assign a crucial role to both perception-action and linguistic experience for abstract words.

Imaging movement-related activity in medicated Parkin-associated and sporadic Parkinson's disease

Treatment-related motor complications such as dyskinesias are a major problem in the long-term management of Parkinson's disease (PD). In sporadic PD, a relatively early onset of the disease is known to be associated with an early development of dyskinesias. Although linked with early onset, patients with Parkin-associated PD often show a stable long-term response to dopaminergic therapy without developing treatment-induced motor complications. Therefore, we reasoned that this difference in vulnerability to develop dyskinesias under long-term dopaminergic therapy may be associated with differences in movement-related activation patterns in Parkin-associated compared to sporadic PD. To test this hypothesis, medicated non-dyskinetic patients with either Parkin-associated or sporadic PD underwent functional magnetic resonance imaging (fMRI) while performing externally specified or internally selected movements. Patients with Parkin-associated and sporadic PD showed no difference in movement-related activation patterns. Moreover, the covariates 'age' and 'disease duration' similarly influenced brain activation in both patient groups. The present finding suggests that a stable long-term motor response in some patients with Parkin-associated PD may not be related to differences in cortical recruitment. In conclusion, our findings corroborate a substantial pathophysiologic overlap between Parkin-associated and sporadic PD and lend further support to the notion that Parkin-associated PD is a suitable genetic model for sporadic PD.

Age-independent activation in areas of the mirror neuron system during action observation and action imagery. A fMRI study

PURPOSE

Recent studies have found age-related BOLD signal changes in several areas of the human brain. We investigated whether such changes also occur in brain areas involved in the processing of motor action observation and imagery.

METHODS

Functional magnetic resonance imaging with an experimental paradigm in which motor acts had to be observed and/or imagined from a first person perspective was performed in twenty-six subjects.

RESULTS

In line with previous work action observation and imagery induced BOLD signal increases in similar areas, predominantly in the premotor and parietal cortex. In contrast to young subjects the elderly displayed a stronger activity in most activated brain areas indicative of compensatory activity for the age-related decline of neural structures. Importantly, activity in the ventrolateral premotor cortex and inferior parietal cortex, seminal areas of the mirror neuron system, did not exhibit activity changes as a function of age.

CONCLUSION

These findings suggest that activity within the mirror neuron system is not age dependent and provide a neural basis for therapeutical interventions and novel rehabilitation treatments such as video therapy.