Temporal dynamics and mechanisms of oscillatory pattern reinstatement in human episodic memory

Michelmann, Sebastian (2018). Temporal dynamics and mechanisms of oscillatory pattern reinstatement in human episodic memory. University of Birmingham. Ph.D.

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Abstract

A fundamental question in the investigation of episodic memory is how the human brain represents information from the past.

This thesis introduces a new method that tracks content specific representations in rhythmic fluctuations of brain activity (i.e. brain oscillations). It is demonstrated that a frequency band centred at 8 Hz carries information about remembered stimulus content. This is shown in human electrophysiological recordings during
episodic memory formation and retrieval.

Strong and sustained power decreases consistently mark this 8 Hz frequency band; successful memory encoding and retrieval are associated with power decreases in low frequencies (<30 Hz) throughout this thesis and in numerous former studies. The presented results link power decreases to the reinstatement of oscillatory patterns in sensory specific areas for the first time and therefore implicate them in the representation of information.

Finally, the temporal dynamics of recollection are investigated by tracking information from distinct sub-events in continuous episodic memories. In behavioural and neural data, memory replay is faster than perception and takes place in a forward direction. Herein, fragments of fine-grained temporal patterns are reinstated; yet, subjects can skip flexibly between sub-events. Leveraging oscillatory mechanisms to track information can
therefore identify episodic memory replay as a dynamic process.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):