Abstract
Theta-burst stimulation (TBS) can be a non-invasive technique to modulate cognitive functions, with promising therapeutic potential, but with some contradictory results. Event related potentials are used as a marker of brain deterioration and can be used to evaluate TBS-related cognitive performance, but its use remains scant. This study aimed to study bilateral inhibitory and excitatory TBS effects upon neurocognitive performance of young healthy volunteers, using the auditory P300’ results. Using a double-blind sham-controlled study, 51 healthy volunteers were randomly assigned to five different groups, two submitted to either excitatory (iTBS) or inhibitory (cTBS) stimulation over the left dorsolateral pre-frontal cortex (DLPFC), two other actively stimulated the right DLPFC and finally a sham stimulation group. An oddball based auditory P300 was performed just before a single session of iTBS, cTBS or sham stimulation and repeated immediately after. P300 mean latency comparison between the pre- and post-TBS stimulation stages revealed significantly faster post stimulation latencies only when iTBS was performed on the left hemisphere (p = 0.003). Right and left hemisphere cTBS significantly delayed P300 latency (right p = 0.026; left p = 0.000). Multiple comparisons for N200 showed slower latencies after iTBS over the right hemisphere. No significant difference was found in amplitude variation. TBS appears to effectively influence neural networking involved in P300 formation, but effects seem distinct for iTBS vs cTBS and for the right or the left hemisphere. P300 evoked potentials can be an effective and practical tool to evaluate transcranial magnetic stimulation related outcomes.
Highlights
Transcranial magnetic stimulation (TMS) has become an essential tool for manipulation of cortical activity, thereby allowing the study of the functional organization of the human brain [1]
When we evaluate the outcomes through a multiple comparisons test, P300 latency over Pz results showed significant differences between the sham group and the left iTBS group (p = 0.024), sham and left cTBS goups (p = 0.001) and between sham and right cTBS groups (p = 0.042)
Reaction times behaved differently with faster reaction times in the excitatory and sham groups, but with no significant changes in the inhibitory groups. Using both inhibitory and excitatory Theta-burst stimulation (TBS) protocols, we found that the parietal P300 showed significantly slower latencies after cTBS stimulation bilaterally but the parietal P300 responses were significantly faster only after iTBS over the left cortex
Summary
Transcranial magnetic stimulation (TMS) has become an essential tool for manipulation of cortical activity, thereby allowing the study of the functional organization of the human brain [1]. Theta-burst influence on event-related brain potentials cognitive functions, both in healthy and pathologic brain. Research focusing upon the cognitive therapeutic potential of rTMS over the last years has shown contradictory results, thereby perpetuating some doubts over its mechanisms [7, 8]. Theta-burst stimulation (TBS) is a form of patterned rTMS which has some advantages including lower stimulation intensity, a short stimulation period and a more prolonged after-effect as compared to other rTMS protocols, both the excitatory (iTBS) and the inhibitory (cTBS) forms [9], and is regarded by some authors to be safer than traditional rTMS [4, 10]
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