Dorsolateral Premotor Areas Research Articles

Connectivity of the frontal and anterior insular network: a cortico-cortical evoked potential study.

OBJECT The frontal and insular fiber network in humans remains largely unknown. This study investigated the connectivity of the frontal and anterior insular network in humans using cortico-cortical evoked potential (CCEP). METHODS This retrospective analysis included 18 patients with medically intractable focal epilepsy who underwent stereoelectroencephalography and CCEP. Alternating 1-Hz electrical stimuli were delivered to parts of the frontal lobe and anterior insula (prefrontal cortex [PFC], ventrolateral and dorsolateral premotor area [vPM and dPM, respectively], presupplementary motor area [pre-SMA], SMA, frontal operculum, and anterior insula). A total of 40-60 stimuli were averaged in each trial to obtain CCEP responses. The distribution of CCEP was evaluated by calculating the root mean square of CCEP responses. RESULTS Stimulation of the PFC elicited prominent CCEP responses in the medial PFC and PMs over the ipsilateral hemisphere. Stimulation of the vPM and dPM induced CCEP responses in the ipsilateral frontoparietal areas. Stimulation of the pre-SMA induced CCEP responses in the ipsilateral medial and lateral frontal areas and contralateral pre-SMA, whereas stimulation of the SMA induced CCEP responses in the bilateral frontoparietal areas. Stimulation of the frontal operculum induced CCEP responses in the ipsilateral insula and temporal operculum. CCEPs were observed in the ipsilateral medial, lateral frontal, and frontotemporal operculum in the anterior insular stimulation. Stimulation of the vPM and SMA led to the network in the dominant hemisphere being more developed. CONCLUSIONS Various regions within the frontal lobe and anterior insula were linked to specific ipsilateral and contralateral regions, which may reflect distinct functional roles.

Changes in Excitability of the Human Motor Cortex Face Area by Observing Speech

Language is the most important communicative tool with substantial evolution in the process of human phylogenetic development. Language processing in humans occurs in a distributed network of brain areas including the superior temporal gyrus which functionally links with the posteroinferofrontal area (including Broca’s area) and the dorsolateral premotor area. This network forms a sensory-motor transformation pathway to map speech perception onto speech production processes [1] [2], which has strong overlap with the putative mirror neuron system (MNS). The MNS is considered to play an important role in unifying action perception and motor execution. The theory of perception-execution matching predicts that observation of motor action should lead to an increase of excitability in the primary motor cortex (M1) representations involved in the observed action. Indeed, motor evoked potential (MEP) amplitude in hand muscles increases during observation of hand and arm movements [3] [4], and MEP amplitude of facial muscles involved in speech production increases when observing speech-related lip movements [5] [6], or even when listening to speech [6] [7]. Furthermore, recent studies also provided evidence for a role of inhibitory mechanisms to prevent overt motor activation during action observation [8] [9].

Gaze-related mimic word activates the frontal eye field and related network in the human brain: An fMRI study

This is an fMRI study demonstrating new evidence that a mimic word highly suggestive of an eye gaze, heard by the ear, significantly activates the frontal eye field (FEF), inferior frontal gyrus (IFG), dorsolateral premotor area (PMdr) and superior parietal lobule (SPL) connected with the frontal–parietal network. However, hearing a non-sense words that did not imply gaze under the same task does not activate this area in humans. We concluded that the FEF would be a critical area for generating/processing an active gaze, evoked by an onomatopoeia word that implied gaze closely associated with social skill. We suggest that the implied active gaze may depend on prefrontal–parietal interactions that modify cognitive gaze led by spatial visual attention associated with the SPL.

The functional role of dorso-lateral premotor cortex during mental rotation: An event-related fMRI study separating cognitive processing steps using a novel task paradigm

Subjects deciding whether two objects presented at angular disparity are identical or mirror versions of each other usually show response times that linearly increase with the angle between objects. This phenomenon has been termed mental rotation. While there is widespread agreement that parietal cortex plays a dominant role in mental rotation, reports concerning the involvement of motor areas are less consistent. From a theoretical point of view, activation in motor areas suggests that mental rotation relies upon visuo-motor rather than visuo-spatial processing alone. However, the type of information that is processed by motor areas during mental rotation remains unclear. In this study we used event-related fMRI to assess whether activation in parietal and dorsolateral premotor areas (dPM) during mental rotation is distinctively related to processing spatial orientation information. Using a newly developed task paradigm we explicitly separated the processing steps (encoding, mental rotation proper and object matching) required by mental rotation tasks and additionally modulated the amount of spatial orientation information that had to be processed. Our results show that activation in dPM during mental rotation is not strongly modulated by the processing of spatial orientation information, and that activation in dPM areas is strongest during mental rotation proper. The latter finding suggests that dPM is involved in more generalized processes such as visuo-spatial attention and movement anticipation. We propose that solving mental rotation tasks is heavily dependent upon visuo-motor processes and evokes neural processing that may be considered as an implicit simulation of actual object rotation.

The role of the basal ganglia in bimanual coordination

The functional anatomical role of the basal ganglia in bimanual coordination is unknown. Utilizing functional MRI (fMRI) at 3 T, we analyzed brain activity during three different typing tasks. The first task consisted of typing with parallel finger movements (moving left to right with four fingers on both hands). The second task was mirror movements (moving little finger to index finger on both hands), and the third task compared a resting condition with right-handed unimanual typing (moving little finger to index finger). Task dependent BOLD activity in the supplementary motor area (SMA) and dorsolateral premotor areas was observed. In addition, activation patterns were present in the cerebellar vermis during bimanual coordination tasks, with greater activation in the parallel than in the mirror condition. Finally, we also identified activity in the putamen during the tasks described above. Interestingly, putaminal activity was greatest during the period of motor task initiation, and activity during this period was greatest in the parallel condition. Our results suggest a critical role of the basal ganglia in the neural control of bimanual coordination.

Spatiotemporal brain dynamics in response to muscle stimulation

The objective of the present study was to assess the spatiotemporal scenario of brain activity associated with sensory stimulation of the abductor pollicis brevis muscle. Spatiotemporal dipole models, using realistic individual boundary element head models, were built from somatosensory evoked potentials (SEPs; 64 Ch. EEG) to nonpainful and painful intramuscular electrostimulation (IMES) as well as to cutaneous electrostimulation delivered to the distal phalanx of the thumb. Nonpainful and painful muscle stimuli resulted in activation of the same brain regions. In temporal order, these were: the contralateral primary sensorimotor cortex, contralateral dorso-lateral premotor area (PM), bilateral operculo-insular cortices, caudal cingulate motor area (CMA), and posterior cingulate cortex/precuneus. Brain processing induced by muscle sensory input showed a characteristic pattern in contrast to cutaneous sensory input, namely: (1) no early SEP components to IMES; (2) an initial IMES component likely generated by proprioceptive input is not present for digit stimulation; (3) one source was located in the PM only for IMES. This source was unmasked by the lower stimulus intensity; (4) a source for IMES was located in the contralateral caudal CMA rather than being located in the cingulate gyrus. Cerebral sensory processing of input from the muscle involved several sensory and motor areas and likely occurs in two parallel streams subserving higher order somatosensory processing as well as sensory–motor integration. The two streams might on one hand involve sensory discrimination via SI and SII and on the other hand integration of sensory feedback for further motor processing via MI, lateral PM area, and caudal CMA.

Cerebral midline structures in bimanual coordination.

In six healthy right-handed volunteers, we compared the cerebral activation pattern related to unimanual right- and left-hand movements and to bimanual in-phase and anti-phase movements using functional magnetic resonance imaging (fMRI). Internally paced unimanual finger-to-thumb opposition movements led to a strong contralateral activation of primary sensorimotor areas in all six subjects. Midline activity was lateralized to the left side during right-hand movements, but to both sides during left-hand movements. Activity patterns of bimanual in-phase movements resembled the combined activity patterns of the two unimanual conditions: right and left hemispheric activations of the primary sensorimotor cortices and predominantly left-sided medial frontal activity. In contrast, during anti-phase movements, we observed a clear increase in activity, in both right and left frontal midline areas and in right hemispheric, mainly dorsolateral premotor areas compared to in-phase movements. These results indicate that frontal midline activity is not specific for bimanual movements per se. It can already be involved during simple unimanual movements but becomes progressively more involved during more complex aspects of movement control.