Premotor Cortex Lesions Research Articles

Perioperative seizure in patients undergoing brain mapping under awake craniotomy for language-related eloquent region gliomas: a prospective study.

Awake craniotomy (AC) is standard of care for lesions of eloquent brain areas. One important complication during AC is occurrence of intraoperative seizure (IOS), reported to occur among 3.4-20% of the patients. In this study, we report our experience with IOS during AC for resection of gliomas of the language eloquent regions and evaluate the predisposing factors and consequences. Patients who underwent AC for language related regions of the dominant hemisphere from August 2018 to June 2021 were enrolled. The rate of IOS during AC and relationship between predisposing factors and IOS were evaluated. Sixty-five patients were enrolled (mean age: 44.4±12.5 years). Among 6 patients with IOS (9.2%), only one needed conversion to general anesthesia (GA) due to repeated seizures; while in the remaining 5, AC accomplished successfully despite one seizure attack in the awake phase. Tumor location (especially premotor cortex lesions, P=0.02, uOR:12.0, CI: 1.20-119.91), higher tumor volume (P=0.008, uOR: 1.9, CI: 1.06-1.12) and a functional tumor margin during surgery (P=0.000, uOR: 3.4, CI: 1.47-12.35) were significantly linked with IOS. Occurrence of IOS was associated with a longer ICU stay after surgery and worse immediate neurological outcome, but had no impact on the late neurological status. IOS can usually be managed during AC without need to converting to GA. Those with larger tumors, frontal premotor lesions and positive brain mapping are susceptible to IOS. Early neurological deterioration observed after IOS, seems to be transient with no major long-term consequence on the neurological outcome.

To Move or Not to Move? Functional Role of Ventral Premotor Cortex in Motor Monitoring During Limb Immobilization

Anatomo-clinical evidence from motor-awareness disorders after brain-damages suggests that the premotor cortex (PMC) is involved in motor-monitoring of voluntary actions. Indeed, PMC lesions prevent patients from detecting the mismatch between intended, but not executed, movements with the paralyzed limb. This functional magnetic resonance imaging study compared, in healthy subjects, free movements against blocked movements, precluded by a cast. Cast-related corticospinal excitability changes were investigated by using transcranial magnetic stimulation. Immediately after the immobilization, when the cast prevented the execution of left-hand movements, the contralateral right (ventral) vPMC showed both increased hemodynamic activity and increased functional connectivity with the hand area in the right somatosensory cortex, suggesting a vPMC involvement in detecting the mismatch between planned and executed movements. Crucially, after 1 week of immobilization, when the motor system had likely learned that no movement could be executed and, therefore, predictions about motor consequences were changed, vPMC did not show the enhanced activity as if no incongruence has to be detected. This can be interpreted as a consequence of the plastic changes induced by long-lasting immobilization, as also proved by the cast-related corticospinal excitability modulation in our subjects. The present findings highlight the crucial role of vPMC in the anatomo-functional network generating the human motor-awareness.

Apraxia Impairs Intentional Retrieval of Incidentally Acquired Motor Knowledge

Apraxia caused by left hemispheric stroke typically impairs skilled sequential movements. After stroke, apraxic patients need to reacquire motor skills by motor learning. The current study assessed for the first time incidental motor sequence learning in apraxic patients. Forty-eight human subjects (henceforth called "patients") with left hemispheric stroke affecting the middle cerebral artery territory (18 with apraxia and 30 without apraxia) and 17 age-matched healthy controls were tested on a visuomanual serial reaction time task. Subjects performed four blocks consisting of repetitions of a complex six element sequence containing ambiguous pairwise transitions before a new and unfamiliar sequence was introduced in block 5. Reaction time (RT) disadvantages in this fifth block indicated incidental sequence-specific motor learning. The intentional retrieval of the learned motor knowledge was assessed subsequently with a free recall task. Voxel-based lesion-symptom mapping (VLSM) was performed to investigate for the first time the lesion correlates of deficits in learning and retrieving sequential motor knowledge. Despite generally prolonged RTs, apraxic patients showed sequence-specific motor learning as could be observed in nonapraxic patients and healthy controls. However, apraxic patients showed reduced intentional retrieval of the learned sequence. VLSM revealed that impaired intentional retrieval of motor sequence knowledge resulted from dorsal premotor cortex lesions. Apraxic patients showed a dissociation of preserved incidental motor (sequence) learning and deficient intentional retrieval of this incidentally learned motor knowledge. The data suggest that novel approaches for treating apraxia should focus on incidental motor learning, but that automatic rather than intentional retrieval strategies should be enforced.

Ventral premotor cortex lesions disrupt learning of sequential grammatical structures

IntroductionRecent functional magnetic resonance imaging (fMRI) evidence shows differential involvement of the inferior frontal gyrus (IFG) and the ventral premotor cortex (PMv) in syntactic processing. Our main goal is to specify the precise role of the PMv in the processing of sequential structures and whether these processes are a necessary prerequisite for the successful acquisition of grammatical structure. MethodsWe tested patients with PMv lesions in an artificial grammar (AG) learning task, including correct sentences and sentences with violations of local (referring to adjacent elements within an AG string) and long-distance dependencies (incorporating recursive structures). In addition to performance measures event-related potentials to these violations were recorded. Results and conclusionsCompared to matched controls, patients displayed impaired acquisition of the AG. This impairment was more pronounced for local than for long-distance dependencies. This effect was paralleled by a selective reduction of the P600 component in response to violations of local dependencies. Most importantly, the P600 elicited by violations of long-distance dependencies was comparable between groups. Together, behavioral and ERP results indicate a PMv involvement in processing local sequential information.

Role of the premotor cortex in leg selection and anticipatory postural adjustments associated with a rapid stepping task in patients with stroke

The premotor cortex (PMC) plays an important role in selecting and preparing for movement. This study investigates how stroke-induced PMC lesions affect stepping leg selection and anticipatory postural adjustments (APAs) preparation. Fifteen hemi-paretic patients (eight with PMC lesions (PMC Lesion) and seven PMC spared (PMC Spared)) and eight age- and sex-matched healthy adults participated in the study. The subjects performed rapid forward stepping with the right or left leg under simple and choice reaction time conditions. The percentage of trials in which the subject showed the correct initial vertical ground reaction force pattern before lift-off of the stepping leg indicated the accuracy in selecting the designated stepping leg. The latency of bilateral contractions in the tibialis anterior (TA) and the reaction time (RT) of the stepping leg represented the time needed to prepare for stepping-related APAs and stepping movement, respectively. All three groups demonstrated a similar rate of accuracy of the stepping leg selection under both conditions. However, in both conditions, the PMC Lesion group exhibited a longer RT and TA contraction latency of the affected leg than the healthy and PMC Spared groups. The PMC Lesion group also presented a longer TA contraction latency of the unaffected leg than the healthy group in both conditions. These results suggest that the PMC is involved in APAs associated with leg stepping movement and that a PMC lesion in one hemisphere impairs APAs of both the contralateral and ipsilateral legs during stepping.

PREMOTOR CORTEX AND CONDITIONAL MOTOR LEARNING IN MAN

The role of premotor cortex (PMC) in conditional motor learning tasks in man was investigated. Patients with PMC lesions had to learn to associate 6 different visual, tactile or auditory stimuli with 6 different arm movements which were previously rehearsed (Task A). A comparative task involved an association between the same set of sensory stimuli and 6 spatial locations (Task B). Patients with PMC lesions were only impaired when they had to recall a movement from memory on the basis of a sensory cue (Task A), but not for an association involving spatial location (Task B). This indicates that the PMC plays a role in sensory conditional motor learning.

Premotor cortex and the retrieval of movement.

It is argued that the premotor cortex plays a crucial role in the retrieval of movement. Monkeys with bilateral lesions in premotor cortex were found to be impaired at selecting between two movements on the basis of visual cues. This was true whether the visual cue was present at the time of response or was no longer visible. Yet other monkeys with bilateral lesions in dorsal premotor cortex had little difficulty in remembering a movement if they had just been forced to make it a few seconds earlier. It is suggested that the premotor cortex is involved in the process of translation from a visual or auditory cue to an associated movement.

Cues for movement in monkeys (Macaca mulatta) with lesions in premotor cortex.

Cues for movement in monkeys (Macaca mulatta) with lesions in premotor cortex.