13 Time Perception

Question 1

3 meanings of time

Answer 1

• natural time: concept of time as medium or dimension
• clock time: quantifiable units
• subjective time: subjective feeling of both the passage of time and how much time has passed

Question 2

subjective time

Answer 2

• construct by the brain
• organs and brain don’t aspire to represent objective outside world
• allows us to feel natural and clock time
• subjective experience is influenced by biology
• subjective time governed by underlying physiological processes

Question 3

5 influences on time perception

Answer 3

• Motivation
• Attention
• sensory change
• novelty
• emotion

Question 4

Role of midbrain dopamine neurons

Answer 4

• essential for voluntary movement, reward processing, working memory
• encode reward prediction error (reinforcement learning)
• DA neurons respond less at times when rewards and reward-predicting cues are more expected (receive temporal information)
• manipulating DAergic system disrupts timing behavior (may directly modulate timing)
• dopaminergic neurons control temporal judgements on a time scale of seconds

Question 5

How do dopamine neurons control judgement of time?

Answer 5

• pharmacogenetic suppression of dopamine neurons decreased behavioral sensitivity to time
• dopamine neurons encoded information about trial-to-trial variability in time estimates
• transient activation or inhibition of dopamine neurons influences time estimation
• activation of DA neurons slows down time estimation

Question 6

What is explicit timing?

Answer 6

• estimate of stimulus duration or interstimulus interval
• perceptual discrimination of timing: decide whether one stimulus/ISI duration is shorter or longer than another
• motor timing: represent timed duration/ISI with sustained, delayed, or periodic motor act (e.g. paced finger tapping task)

Question 7

What is implicit timing?

Answer 7

• regular temporal pattern of sensory stimuli or motor responses can be used to achieve non-temporal task goals
• e.g., velocity parameters of an approaching vehicle can be used to estimate when it will reach a certain location

Question 8

What is the pacemaker-accumulator model

Answer 8

• model of duration estimation based on internal clock model
• stimulus triggers accumulator to start counting pulses emitted by internal pacemaker
• pulse tally is passed into working memory for comparison with previously stored pulse tally
• response according to comparison
• attentional switch: the less attention paid, the fewer pulses accounted for by accumulator -> underestimation of time
• neurophysiologists seek more neurally plausible model

Question 9

Which brain areas are involved in time perception?

Answer 9

• Cerebellum
• prefrontal cortex (PFC)
• basal ganglia

Question 10

Cerebellum and time perception

Answer 10

comparison between patients with Parkinson and cerebellar/cortical lesions:
- increased motor timing variability and impairments in accuracy in explicit timing in cerebellar patients
- supramodal role for cerebellum in timing
- TMS evidence supports results while suggesting putative functional specialization of lateral and medial regions for auditory and visual time representations
- deficits in implicit timings in cerebellar patients as well
- lesions to lateral regions of cerebellum cause motor timing deficits

Question 11

prefrontal cortex and time perception

Answer 11

hazard function
- probability of event occurring rises with increasing time it’s not occurring
- increase in subjective sense of temporal expectation (faster RTs)
- lesions to right PFC lead to loss of RT benefit of long fore-periods
- right PFC has feedback role to update temporal predictions

Question 12

basal ganglia and time perception

Answer 12

• less important than cerebellum in making temporal predictions (PD patients no difficulty in implicit timing)
• PD patients show deficits in explicit timing (perceptual and motor timings)
• impairments correlate with disease severity
  migrations effect
• off medication, PD patients overestimated pre-learned short durations and underestimated long ones
• both estimates tended to migrate towards central common value
• motor and perceptual timing tasks activate lateral (putamen) and medial regions (caudate and globus pallidus), however most often activated with variety of anatomically discrete cortical regions

Question 13

coincidence-detection model

Answer 13

• basal ganglia might monitor activity of functionally integrated network
• activation of thalamo-corticalstriatal circuits (BG, PFC and posterior parietal cortex)
• BG signals patterns of activity in working memory
• timing based on coincidental activation of different neural populations
• timing circuit is continuous-event, cognitive controlled timing system requiring attention
• probably not limited to temporal processing

Question 14

biological rhythms and timings

Answer 14

• infradian rhythm: >24h, e.g. menstrual cycle, seasonal hormonal changes like testosterone
• circadian rhythm: 24h, e.g. sleep-wake cycle
• ultradian rhythm: <24h, e.g. sleep stages
• interval timing: seconds to minutes/hours, e.g. decision making, time estimation
• ms timing: >1s, e.g. speech, motor control

Question 15

circadian rhythm

Answer 15

• center: suprachiasmatic nucleus (SCN) in hypothalamus: regulates neuronal activity, body temperature, sleep-wake-cycle, hormonal signals
• set by genetic and environmental factors (e.g. light, social cues, meal time, work schedule)

Question 16

circadian rhythm early development

Answer 16

• emerges within first several months after birth
• body temperature rhythms immediately after birth
• sleep-wake rhythm between 3-6 months, consolidation within first year by increased melatonin secretion
• nocturnal sleep coupled with sunset first, then with family bedtime after a few months (environmental factor)
• change in melatonin levels and body temperature (peak in childhood)

Question 17

circadian rhythm in adolescence

Answer 17

• rhythmic changes during adolescence
• phase delay in sleep-wake cycle and melatonin dependent on gonadal hormones and environmental factors: social pressure, less parental involvement in bedtime routine
• more sensitive to light exposure at night at age 9-14 (early adolescents) compared to age 11-15 (late adolescents)
• early morning light exposure suppresses melatonin levels, but no age differences

Question 18

circadian rhythm in adulthood

Answer 18

• earlier sleeping hours compared to adolescence
• shorter sleep durations
• loss of amplitude in melatonin, cortisol, body temperature

Question 19

interval timing studies with infants

Answer 19

• 1-month old infants already show learned pupillary reflex to light, even though no light at expected point in time
• 10-month old infants show same mismatch negativity as adults
• 6-10 month old infants show increased looking time when repeated duration of an event differs
• ability to discriminate changes in duration is proportional to length of standard duration
• infants have primitive sense of time
• cerebral mechanism matures early or/and is functional at early age

Question 20

improvement in time sensitivity during childhood

Answer 20

• increase in Weber ratio after 4s
• the lower Weber ratio, the more sensitive to time
• time processing also depends on working memory, attention, and other executive functions like inhibition of motor responses, selective attention, sustained attention

Question 21

explicit time judgement in childhood

Answer 21

• explicit time judgement develops between age 3-6
• 3-5-year old children can estimate intervals of events repeatedly experienced but unaware of its time and relevance when they encouter new event
• children can make explicit judgements of time at about 7 years of age

Question 22

implicit time judgement in childhood

Answer 22

• earlier maturation of striatum => early timing abilities in infants, implicit time judgements
• longer durational judgements for anger at age 3, no developmental difference between age groups
• emotional states can distort time judgements
• related to early development of striatum and dopaminergic system

Question 23

fMRI studies with children

Answer 23

• with increasing age progressive recruitment of later maturing left hemisphere and lateralized fronto-parieto-striato-thalamic networks known to mediate time discrimination in adults
• earlier developing brain regions such as ventromedial prefrontal cortex, limbic and paralimbic areas, and cerebellum subserve fine-temporal processing functions in children and adolescents
• Time processesing from relatively early developed middle frontal limbic and posterior brain regions to fronto-striatal and parietal regions with development
• parallel with increase in attentional capacity with maturation which also affects timing judgment

Question 24

time perception in ADHD

Answer 24

• timing deficits in different temporal tasks
• reduced activity in right inferior and dorsolateral prefrontal cortex and anterior cingulate gyrus
• underlining importance of fronto-striatal system’s development in time processing