The effect of cortical repetitive transcranial magnetic stimulation on cognitive event-related potentials recorded in the subthalamic nucleus

Abstract

We studied whether the cognitive event-related potentials (ERP) in the subthalamic nucleus (STN) are modified by the modulation of the inferior frontal cortex (IFC) and the dorsolateral prefrontal cortex (DLPFC) with repetitive transcranial magnetic stimulation (rTMS). Eighteen patients with Parkinson's disease who had been implanted with a deep brain stimulation (DBS) electrode were included in the study. The ERPs were recorded from the DBS electrode before and after the rTMS (1 Hz, 600 pulses) over either the right IFC (10 patients) or the right DLPFC (8 patients). The ERPs were generated by auditory stimuli. rTMS over the right IFC led to a shortening of ERP latencies from 277 +/- 14 ms (SD) to 252 +/- 19 ms in the standard protocol and from 296 +/- 17 ms to 270 +/- 20 ms in the protocol modified by a higher load of executive functions (both P < 0.01). The application of rTMS over the DLPFC and the sham stimulation over the IFC showed no significant changes. The shortening of ERP latency after rTMS over the right IFC reflected the increase in the speed of the cognitive process. The rTMS modulation of activity of the DLPFC did not influence the ERP. Connections (the IFC-STN hyperdirect pathway) with the cortex that bypass the BG-thalamocortical circuitries could explain the position of the STN in the processing of executive functions.

Non-invasive brain stimulation of the right inferior frontal gyrus may improve attention in early Alzheimer's disease: A pilot study

“…We previously showed that rTMS applied over the IFG enhanced cognitive speed in a group (n = 10) of non-demented Parkinson's disease (PD) subjects regardless of cognitive load [46]. In the same vein, rTMS applied over the right IFG decreased the latency of P3 waves recorded in the subthalamic nucleus of PD subjects during both simple and dual executive tasks [4]. We hypothesized that similar aftereffects would be achieved in our AD group.…”

“…The connection between the IFG and subthalamic nucleus, referred to as a hyperdirect [22], JLOJudgment of Line Orientation Test [6], RCFT -Rey-Osterrieth Complex Figure Test (copy) [33], MAST -Mississippi Aphasia Screening Test (Expressive, Receptive, and Total indexes) [26], ADL -Activities of Daily Living (FAQ -Functional Activities Questionnaire) [5], MADRS -Montgomery-Asberg Depression Rating Scale [34]. pathway, can play a role in executive processing [4] in the PD population and also in AD patients.…”

“…[16,25,27,32]). Based on our previous functional magnetic resonance imaging (fMRI) and rTMS results in patients with degenerative brain diseases, we chose two cortical areas to study: the right inferior frontal gyrus (IFG) in order to modulate attention and cognitive speed [4,43,44,46] and the right superior temporal gyrus (STG) in order to manipulate visual processing, visual memory encoding, and recognition [7,27] in AD population. These brain areas are easily accessible by rTMS when the coil is navigated by a frameless stereotaxy.…”

Involvement of the subthalamic nucleus in cognitive functions — A concept

“…Recent studies have demonstrated that specific oscillations in the STN are involved in cognitive and behavioral information processing: action representation is mediated through 13-35 Hz oscillations, decision making processes through 5-12 Hz oscillations, limbic and emotional information through 8-12 Hz oscillations [58]. Evoked local field potentials related to executive functions and attention were found in the STN during performance of both visual and auditory cognitive paradigms [13,59,60]. These papers by our group indicate a specific, task-related involvement of the STN in cognitive activities.…”

“…Direct cortical projections to the STN were described [10], but they were considered to be sparse, and therefore regarded as less important. According to recent views, the STN has not only a crucial position in the indirect pathway of the BG, but it also receives direct cortical projections, especially from the frontal lobe, namely the primary motor cortex, supplementary motor area, and the dorsal and ventral divisions of the premotor cortex, such as the hyperdirect pathway from the inferior frontal cortex (IFC) [11][12][13][14].…”