Cognition Lecture 16 - Events

Working memory vs Long Term Memory

“Systems of Memory” framework

• Classical view: information storage is separated from the information-processing units

Hierarchical Process Memory

The past is continuously being integrated with the present

• In language, we need to integrate each word with preceding words and sentences with each other

Hierarchical Process Memory (cont)

Organization based on temporal processing windows

• HPM: no separation between information storage and processing, memory is integrated with processes

(cont)

Scrambling stories to confuse your brain

• If a brain region has a specific (or maximum) time-integration window for stimuli, it would be disrupted by scrambling above that specific timescale

(cont 2)

Different regions integrate information over different timescales

• Temporal receptive windows (TRW) are the time equivalent of retinotopic spatial receptive fields

(cont 3)

Electrophysiology evidence in non-human primates

• Temporal receptive windows (TRM) are the temporal equivalent of retinotopic spatial receptive fields

Experiencing the World as Stories

Our naturalistic sensory input is complex, but structured

• *TV show example

Quantifying the Elements of a Story

From words to sentences to scenes to events

• Events: points in the movie when there is a major change in topic, location, or time

Events in Naturalistic Cognition

Consistent chinks of narrative experience

Event boundaries

point in the narrative / neural response with a major change in topic, location, or time

Assumption 1

an event is semantically consistent and elicits a consistent pattern of neural activity

Assumption 2

each event pattern is unique and brain regions transition between events (and patterns)

Neural Event Discovery: HMM

Hidden Markov Model for (neural) event segmentation

Number of Neural Events Varies Across Cortex

Posteromedial cortex (PMC) event structure similar to perception

• The brain is building increasingly complex, longer TRW patterns that better reflect structure in the world

• Correlated with the region’s temporal receptive window (TRW)

Why are event boundaries important?

Event boundaries trigger hippocampal encoding signals

• Strength of encoding signal is correlated with reinstatement quality and with better memory for the event

Important takeaway

When an event ends, information in high-level cortical regions is stored as episodic memory

Real Life Experience is a Stream of Events

And they are encoded from / reinstated to cortex at boundaries