Correlates of Time Perception in EEG What does the CNV tell us about subjective duration?
Sophie Herbst
1,2
, Trevor B. Penney , Niko A. Busch
3
1,4
sophie.herbst@hu-berlin.de
EEG Results - Time Dilation by Flicker is reflected in larger CNV amplitude
CNV
Subjective duration & Flicker Frequency
- visual Flicker dilates perceived duration
(Herbst et al., in prep)
- the slower the frequency, the longer subjective
duration, as long as the flicker is visible
> we investigated how differences in
subjective timing are reflected in the CNV
1
time
peak
Methods
Temporal Bisection Task (as in Ng et al. 2011):
- short anchor: 500 ms, long anchor 3500 ms
- probe durations: 7 linearily spaced durations
from 500 - 3500 ms
- visual flicker, three conditions: 4 Hz, 31 Hz, 250 Hz
> Estimation of Point of Subjective Equality (PSE)
for each flicker condition
EEG measurement:
- 64 channels
- reference: averaged mastoids
- offline high-pass filter at 0.05 Hz
- detrending
> Isolation of a CNV component in the ERP
0.4
1
0
0
−1
−1
−2
−2
−3
−3
4 Hz
31 Hz
250 Hz
0
0
-0.4
-0.6
visible flicker invisible flicker
-0.8
-1
0
10
20
30
40
50
60
70
stimulation frequencies [Hz]
80
90
Behavioral Results: Flicker Frequency influences perceived duration
1
time [s]
2
3
**
**
−1.5
−4
4
31 250
frequency [Hz]
CNV at fronto-central channels
2.5
0
EEG Results - Prolonged Duration Judgements lead to larger CNV amplitude
3.5
3
1.5
- CNV amplitude differed between flicker conditions (F(2,28) = 6.81; p <0.05)
- 4 Hz flicker (which also led to longest subjective duration) elicited the largest amplitue,
significantly different from the amplitude in the 250 Hz condition (p < 0.05).
- the 31 Hz condition evoked an intermediate amplitde, but did not differ significantly from
250 Hz
standard duration
threshold
-0.2
mean amplitudes from
0.5 to 1.5 s (longer durations)
1
2
1
0
0
−1
−1
−2
−2
2
1.5
1
0.5
0
4.0
31
250
Stimulation Frequency [Hz]
- PSE differed between flicker conditions
(F(2,45) = 3.69, p = 0.032)
- 4 Hz & 31Hz flicker dilated perceived duration
(p < 0.01) compared to 250 Hz
Conclusions
Visual Flicker dilates subjective duration in a temporal bisection task.
This difference is reflected in the CNV amplitude: frequencies that
produce dilation, also elicite larger CNV amplitudes. Consistently,
trials judged as long across all frequencies show a larger CNV amplitude,
compared with trials judges as short.
Macar, F., Vidal, F., and Casini, L. (1999). The supplementary motor area in motor and sensory
timing: evidence from slow brain potential changes. Experimental Brain Research,
125(3):271-280.
1
0.2
Macar, F. and Vidal, F. (2009). Timing processes: An outline of behavioural and neural indices not systematically considered in timing models. Canadian Journal of Experimental Psychology/Revue canadienne de psychologie exp�erimentale, 63(3):227.
amplitude [μV]
amplitude
mean amplitudes from
1.5 to 2.5 s (longer durations)
−4
0
−2
−3
−3
−4
−4
0
avg number of
trials
“short”
0.6
PSE [s]
+
0.8
duration thresholds [s]
“long”
flicker
fusion
threshold
CNV at fronto-central channels
amplitude [μV]
CNV
- a slow deflection in the ERP
- described as a neural correlate of subjective timing
- CNV amplitude is seen as a signature of a temporal
accumulation process (Macar &Vidal 2009)
- larger amplitudes ~ longer subjective duration (Macar et al. 1999)
- Recently, the association between the CNV and temporal
accumulation has been questioned (van Rijn, 2011)
*
Background
–
1) Berlin School of Mind and Brain, Berlin Germany
2) Humboldt-Universität zu Berlin
3) National University of Singapore
4) Charité Universitätsmedizin Berlin
120
80
40
0
1
time [s]
2
3
long
short
judgment
- CNV amplitudes differed marginally for trials judged
as short versus long (p = 0.07)
0
0.5
1
1.5
2
stimulus duration [s]
2.5
3
3.5
Time Dilation by flicker is reflected in CNV amplitudes, showing that
1) CNV is a signature of subjectve timing
2) The effect of flicker on timing is not solely due to a response bias
Open questions:
- Does the peak latency reflect differences in subjective timing?
- Does the CNV reflect different processes at differnt timeranges?
Ng, K. K., Tobin, S., and Penney, T. B. (2011). Temporal accumulation and decision processes in the
duration bisection task revealed by contingent negative variation. Front Integr Neurosci, 5:77.
van Rijn, H., Kononowicz, T. W., Meck, W. H., Ng, K. K., and Penney, T. B. (2011). Contingent
negative variation and its relation to time estimation: a theoretical evaluation. Front Integr Neurosci,
5:91.