Does Repetitive Transcranial Magnetic Stimulation (rTMS) Cause Amnesia?
No, rTMS does not cause amnesia. The evidence demonstrates that rTMS produces only temporary, task-specific disruptions in cognitive processing during stimulation, with no evidence of persistent anterograde or retrograde memory deficits after treatment completion.
Evidence for Absence of Amnesia
The most definitive evidence comes from direct comparison studies showing no memory deficits after rTMS treatment:
A controlled study comparing rTMS to electroconvulsive therapy (ECT) found that patients who underwent 2 weeks of rTMS treatment (1600 stimuli at 10 Hz daily to the left dorsolateral prefrontal cortex) showed no evidence of anterograde or retrograde memory deficits after treatment, in stark contrast to ECT which caused transient memory impairment 1.
This finding is particularly significant because the study specifically assessed for amnesia-type deficits and found none with rTMS, despite using relatively intensive stimulation parameters 1.
Temporary Cognitive Effects During Stimulation
rTMS can cause transient disruption of cognitive processing only while stimulation is actively being applied:
Meta-analytic evidence from 126 studies shows that online rTMS (applied during cognitive tasks) at 10 Hz and 20 Hz can disrupt accuracy in memory tasks, but these effects are limited to the period of active stimulation 2, 3, 4.
The mechanism is a "virtual lesion" effect where stimulation temporarily interrupts ongoing neural processing, not a lasting impairment of memory formation or retrieval 4.
These disruptions are timing-dependent and frequency-dependent, occurring only when specific parameters are met during active task performance 2, 4.
Key Distinctions
It is critical to distinguish between temporary task disruption and amnesia:
Temporary disruption: High-frequency rTMS (10-20 Hz) can impair performance on memory tasks during the actual stimulation period 4.
Amnesia: A persistent inability to form new memories (anterograde) or recall past memories (retrograde), which does not occur with rTMS 1.
Lower frequencies (≤5 Hz) show minimal effects on cognitive processing even during active stimulation 2, 4.
Clinical Implications
For clinical practice, rTMS can be considered safe regarding memory function:
Offline rTMS (applied before cognitive tasks) shows limited effects on cognitive functioning in healthy adults, with small effect sizes that do not constitute clinically meaningful memory impairment 5.
The effects of rTMS are transient and resolve immediately after stimulation ceases, unlike the persistent retrograde amnesia seen with ECT 1.
Standard therapeutic protocols using rTMS for depression or other conditions do not produce amnesia as a side effect 1.
Important Caveats
While rTMS does not cause amnesia, certain parameters can maximize temporary cognitive disruption:
Higher frequencies (10-20 Hz) are more likely to cause temporary task performance deficits than lower frequencies 4.
Shorter inter-trial intervals are associated with increased disruption during active stimulation 3, 4.
fMRI-guided targeting produces stronger effects than scalp-based targeting, potentially increasing temporary disruption magnitude 3.
These factors are relevant for research applications where temporary disruption is desired, but do not translate to lasting amnesia in clinical applications.