Week2

Timing and Time Perception

• Course: COGS2000, Week 2

Degrees of Time Perception

• Perception of time: varies significantly; influenced by different factors.

• William James: introduced the concept of the 'saddle of the present', which highlights how the perception of time can be fluid.

• Flicker Fusion: describes the break in perception when rapid stimuli create a sense of continuity.

Types of Timing

• Two types of timing:

  • Retrospective Timing: remembering duration after the event.

  • Prospective Timing: tracking time during an event.

• Implicit vs. Explicit Timing:

  • Implicit involves subconscious awareness of time; explicit involves conscious measurement and awareness of time.

  • Timing often involves waiting for a response after perceiving an event.

Tasks for Timing

• Key tasks involved in timing include:

  • Bisection, reproduction, production, temporal generalisation.

    • Each task has different requirements for memory and attention.

  • Simultaneity Judgments: determining whether events occurred together.

  • Temporal Order Judgments: discerning the sequence of events.

  • Passage of Time Judgments: how we perceive time passing during different contexts.

  • Highly contextual and sensitive to variables like when the questions are posed.

  • Time-tradeoff Judgments: evaluation of how time affects choices, such as monetary decisions.

Temporal Discounting

• Example of Delay Preference:

  • Choosing between different monetary rewards over time (e.g. $10 today vs. $12 tomorrow).

• Calculation of values:

  • Comparison allows assessment of value of time versus money and consistency in decision-making related to time.

• Real-world scenario: Trading time in online driver training for avoiding fines.

Brain Hypotheses in Delay Discounting

• Hypothesis Exploration:

  • What brain activity occurs during delay discounting tasks?

  • Considerations include:

    • Future self-projection

    • Delayed gratification

    • Self-control analysis.

fMRI Insights

• General Points:

  • Correlational Data: fMRI results are correlational, not causal.

  • Temporal Limitations: fMRI samples are relatively slow (around 1 second).

  • Technique: Images generated using the magnetic properties of molecules.

MRI Imaging Process

• Static Magnetic Field Application:.

  • Aligns hydrogen atoms to a common plane.

• RF Pulse Application:

  • Alters the alignment of hydrogen atoms enabling imaging based on how they resonate after pulses.

Generating an Image (Steps)

1. Initial 90° RF pulse aligns protons.

2. Protons begin to dephase after the pulse is removed.

3. At mid-time (TE/2), a 180° RF pulse flips their orientation.

4. Protons oscillate to a maximum when they are back in phase, producing an echo for imaging.

Insights on Temporal Discounting

• Brain Activity during Decision Making:

  • Decreased brain activity in specific regions indicates less preference for delayed rewards.

  • Regions affected include:

    • Left inferior frontal gyrus (IFG)

    • Ventral striatum (VS)

    • Anterior cingulate cortex (ACC) and medial prefrontal cortex (mPFC).

• Comparisons made between healthy individuals and those with addiction issues.

Neuroanatomy of Timing

• The correlation of timing decisions in brain regions:

  • Two systems of decision making (objective value vs. subjective).

  • Different brain areas engaged in processing timing and decision-making.

Simultaneity Judgement Tasks

• Nature of tasks: Determine the order and simultaneity of sensory experiences (speed of light vs. sound).

• Critical Differences in Perception Times:

  • Light takes longer to reach the brain than sound, resulting in perceptual lags.

Variable Foreperiods and Temporal Expectations

• Use of variable foreperiods relates to temporal expectations aiding learning over time without formal judgments.

• Key Features of the Task:

  • Hazard function and carryover effects based on previous trials.

(M)EEG Measures

• How (M)EEG monitors brain activity through electrical activity from neurons.

• Recognized for high sample rates compared to other modalities like fMRI.

Impact of Contextual Variables on Timing

• Factors affecting time perception include:

  • Temperature

  • Attention

  • Memory

  • Task difficulty

  • Age

  • Psychological conditions and emotions.

Potential Clocks in the Brain

• Evidence suggests multiple areas can keep time, particularly:

  • Auditory information perceived as lasting longer than visual.

  • Roles of regions like hippocampus, cerebellum, and striatum need further investigation.

Complex Models of Time Perception

• Current biological models highlight dopamine's role in timing, integrating different neuronal pathways for processing events.

• Cortex and Thalamus Integration:

  • Coordination between areas enables the brain's timing capabilities.

Questions for Further Exploration

• Open to queries regarding the neurological underpinnings of timing perception and the models presented.