Brain Stimulation and Elicited Memories

Rickard L. Sjöberg (2023)

Journal: Acta Neurochirurgica
Volume: 165
Pages: 2737–2745
DOI: https://doi.org/10.1007/s00701-022-05307-6

Overview

Since the late 1930s, electrical brain stimulation (EBS) in awake neurosurgical patients has occasionally elicited vivid mental experiences commonly described as memory flashbacks or experiential phenomena. These experiences have often been interpreted as the replay or recovery of authentic autobiographical memories.

In this invited mini-review, Rickard L. Sjöberg critically examines that interpretation and evaluates an alternative explanation: that many EBS-elicited experiences may be synthetic constructions—newly generated mental events that are misinterpreted as memories rather than genuine recollections.

Historical Background: Penfield’s Experiments

In 1934, Wilder Penfield applied a “gentle electrical stimulus” to the superior temporal gyrus of an awake epilepsy patient during surgery at the Montreal Neurological Institute. The stimulation produced vivid auditory experiences.

“These stimulations caused the patient to cry out that she heard a large number of people shouting. Once she said: ‘They are yelling at me for doing something wrong; everybody is yelling.’ On inquiry she said she could hear her mother and brothers.”

Penfield later described these events as experiential phenomena, defining them as cases in which electrical stimulation caused the conscious patient to become aware of a previous experience.

Fragmentary and Uncontrolled Nature of Experiential Reports

Sjöberg emphasizes that EBS-elicited experiences are rarely complete, coherent memories. Instead, they are typically:

• Fragmentary
  
  

• Sensory-specific
  
  

• Context-dependent
  
  

• Lacking verifiable autobiographical detail
  
  

Systematic reviews of the literature show that the type of experience reported often depends on the anatomical site of stimulation, suggesting a perceptual or interpretive origin rather than full memory replay.

The Source Attribution Hypothesis

A central focus of the paper is source attribution error—a well-documented cognitive phenomenon in which individuals misidentify the origin of a mental experience.

According to this hypothesis:

• Electrical stimulation may generate sensory or perceptual signals
  
  

• The brain attempts to interpret these signals
  
  

• The experience is mistakenly labeled as a memory
  
  

This process may be influenced by:

• The stimulation itself
  
  

• The clinical context
  
  

• Interaction with the neurosurgeon
  
  

• Expectations or suggestion
  
  

“There is unfortunately no scientifically validated method that, with a high amount of precision, can distinguish verbal accounts of memories that are ‘synthetic constructions’ from those that are literally true in the absence of independent documentation.”

Controlled Studies and Memory Errors

In contrast to anecdotal reports, controlled experimental studies provide clearer results.

When electrical brain stimulation is applied during memory retrieval tasks:

• Memory accuracy does not improve
  
  

• False recognitions increase
  
  

• Commission errors become more frequent
  
  

• Source monitoring is impaired
  
  

These findings are consistent across stimulation of the superior temporal gyrus and hippocampal regions—areas closely associated with memory processing.

Rather than enhancing memory, EBS appears to disrupt the brain’s ability to correctly identify the source of mental content.

Why Penfield’s Findings Are Rarely Replicated Today

Despite the continued use of awake craniotomy with cortical stimulation, modern neurosurgery rarely reports experiential phenomena.

Possible explanations discussed include:

• Changes in questioning style
  
  

• Reduced suggestive interviewing
  
  

• Improved awareness of cognitive bias
  
  

• Different clinical priorities
  
  

This absence raises further questions about whether early reports reflected memory replay or interpretive constructions influenced by context.

Conclusions

Sjöberg concludes that experiential phenomena elicited by electrical brain stimulation may often be better understood as constructed mental events rather than the replay of stored memories.

“The hypothesis that experiential phenomena may largely be ‘synthetic constructions’ deserves serious consideration.”

The paper does not deny that the brain is involved in memory, but it challenges the assumption that vivid experiences elicited by stimulation necessarily reflect authentic recollection.

Relevance to Consciousness and Dream Studies

These findings have direct relevance for studies of dreaming and consciousness. They demonstrate that:

• Vivid, narrative-like experiences can occur without conscious authorship
  
  

• The brain can generate experiential content without intentional control
  
  

• Perception of memory does not guarantee genuine recall
  
  

This parallels dream states, where structured experiences unfold independently of the waking self and supports broader arguments that conscious experience is not reducible to neural activation alone.

Citation

Sjöberg, R. L. (2023). Brain stimulation and elicited memories.
Acta Neurochirurgica, 165, 2737–2745.
https://doi.org/10.1007/s00701-022-05307-6