What is the Bereitschaftspotential

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What is the Bereitschaftspotential?
Beitrag zu 180241 Freiheit im Kopf - Zur
aktuellen Debatte zwischen Philosophie und
Neurophysiologie Hrachovec, WS 06/07

• Hiroshi Shibasaki and Mark Hallett (2006)
• Clinical Neurophysiol. 172341-2356

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Fig. 1. Waveforms and terminology of
movement-related cortical potentials (MRCPs) from
a single normal subject. Self-initiated left
wrist extension. Average of 98 trials. Reference
(Ref) linked ear electrodes (A1A2). Early
pre-movement negativity (early BP) starts 1.7 s
before the onset of the averaged, rectified EMG
of the left wrist extensor muscle, and is maximal
at the midline central electrode (Cz) and widely
and symmetrically distributed on both
hemispheres. Later negative slope (late BP)
starts 300 ms before the EMG onset and is much
larger over the right central region
(contralateral to the movement). A negative peak
localized at the contralateral central area (C2)
is N-10 or motor potential (MP). Another negative
peak occurring shortly after N-10 is localized
over the midline frontal region and corresponds
to N50 or the frontal peak of motor potential
(fpMP). Shibasaki Hallett (2006) Clinical
Neurophysiol. 172341-2356
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Fig. 2. MRCPs recorded from scalp electrodes in
association with self-paced praxis movements of
the right hand in right-handed normal subjects
(grand average across 8 subjects). Reference
linked ear electrodes. Both for the pantomime of
tool use (transitive shown in grey) and gesture
(intransitive shown in black), BP starts at the
superior parietal region predominantly on the
left as early as 4 s before the movement onset,
and then develops over the inferior parietal
region. About 1 s before the movement onset, a
sharp negative slope is seen over the midline
frontal region and bilateral sensorimotor regions
predominantly on the left. Data of the left
hemisphere shown on the left side.
0.05 lt p lt 0.10, p lt 0.05. cited from Wheaton
et al. (2005a) with permission.
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Fig. 3. Representative waveforms of MRCP and
movement-related magnetic field (MRMF) in
association with self-paced right finger
movements in a right-handed normal subject. Early
BP starts bilaterally about 3 s before the
movement onset, and late BP (NS') is seen over
the contralateral hemisphere starting about
500 ms before the movement onset. On MEG, a sharp
slope is seen only over the contralateral
hemisphere starting about 800 ms before the
movement onset (By courtesy of Dr. Takashi
Nagamine).
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Fig. 4. Epicortically recorded MRCPs associated
with self-paced horizontal saccade. Saccade was
made from the central fixation point to the
visual target placed 25 degrees contralateral to
the implanted electrodes. BP starts in the
supplementary eye field (electrode a5, b5) on the
mesial aspect of the frontal lobe at 2.5 s before
the saccade onset, and then it occurs in the
frontal eye field on the lateral aspect
(electrode B4) with smaller amplitude,
culminating into a sharp negative potential (MP)
cited from Yamamoto et al. (2004) with
permission.
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Fig. 5. Scalp distribution of event-related
desynchronization (ERD) of beta frequency bands
in association with self-paced sequential
movements of the right and left-hand across 9
right-handed normal subjects. In the right-hand
movement, ERD starts over the left central region
about 1.5 s before the movement onset and becomes
bilateral shortly before and during the movement.
In the left-hand movement, ERD is seen
bilaterally from about 1.5 s before the movement
onset and increases toward the movement onset
cited from Bai et al. (2005) with permission.
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beta frequency ?
Fig. 6. Movement-related power change of
electrocorticogram for various frequency bands,
simultaneously recorded from the SMA proper, M1
hand area and S1 hand area which were determined
by electrical stimulation study in a patient with
medically intractable partial epilepsy. The data
for the contralateral hand movement are shown in
thick black line, and those for the ipsilateral
hand movement are shown in thin grey line. ERD
for beta frequency band starts in the SMA proper
about 3.5 s before the movement onset
bilaterally. About 2 s prior to the movement
onset, ERD for high alpha and beta frequency
bands is seen in the M1 hand area bilaterally,
more contralaterally, followed by ERD in the S1
hand area. After the movement, increase of gamma
frequency band (ERS) is seen exclusively in the
contralateral S1 hand area cited from Ohara et
al. (2000a) with permission.
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The BOLD response
Beitrag zu 180241 Freiheit im Kopf - Zur
aktuellen Debatte zwischen Philosophie und
Neurophysiologie Hrachovec, WS 06/07

• (blood oxygen level-dependent response)

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Fig. 1. Model of the dispersion along the venous
flow path. Flow increases, resulting from opening
of sphincters, generate an oxyhemoglobin
concentration change that is carried down the
vascular network. The temporal characteristics of
the MRI signal, related to the local
oxyhemoglobin concentration, are affected by flow
characteristics along the venous flow path, with
incremental signal delays accumulated in
capillary bed, intracortical veins, and pial
vasculature. De Zwart et al. (2005) NeuroImage
24 667-677
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Fig. 1. Vasculature in the brain and the BOLD
effect. Dogil et al. (2002) J. Neuroling. 15
59-90
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Hemodynamic response function
Figure 2 Group average hemodynamic response
curves generated from 19 volunteers. Note the
amplitude and post-stimulus undershoot
differences in these curves. http//www.radiolog
y.northwestern.edu/research/neuro/investigate.cfm
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Haynes Rees (2006) Decoding mental states from
brain activity in humans. Nat. Rev. Neurosci. 7
523-33.
Decoding the contents of visual imagery from
spatially distinct signals in the fusiform face
area (FFA, red) and parahippocampal place area
(PPA, blue). During periods of face imagery (red
arrows), signals are elevated in the FFA whereas
during the imagery of buildings (blue arrows),
signals are elevated in PPA. A human observer,
who was only given signals from the FFA and PPA
of each participant, was able to estimate with
85 accuracy which of the two categories the
participants were imagining (modified, with
permission, from OCraven Kanwisher 2000, J
Cogn Neurosci 12 1013-23).
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Polyn, Natu, Cohen, Norman (2005)
Category-specific cortical activity precedes
retrieval during memory search. Science 310
1963-66.

• Free-recall paradigm
• Subjects were asked to recall studied items in
  the absence of specific cues. Study items were
• Photographs of famous faces,
• Photographs of famous locations, and
• Photographs of common objects.
• Each item was given a name.
• In a free-recall test, subjects were asked to
  recall all studied items, in any order and
  regardless of category.
• fMRI was recorded during recall.

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A neural-network pattern classifier was trained
to discriminate between patterns of whole-brain
activity associated with face, location, and
object stimuli.
Fig. 3. The classifier-derived importance maps.
Each voxel was assigned an "importance value" ...
Voxels with positive importance values are
colored red voxels with negative importance
values are colored blue. The colors fade into
transparency as importance values approach zero,
as shown on the color bar. FG, fusiform gyrus
PG, parahippocampal gyrus MFG, medial frontal
gyrus PC, posterior cingulate MTG, middle
temporal gyrus (24). Polyn, Natu, Cohen, Norman
(2005) Science 310 1963-66
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Fig. 1. Correspondence between the classifier's
estimates of contextual reinstatement and verbal
recalls for a single representative subject...
each time point represents one complete brain
scan (lasting 1.8 s). For each brain scan, the
classifier produced an estimate of the match
between the current testing pattern and each of
the three study contexts (strength of estimate
appears on the y axis). The blue, red, and green
lines correspond to the face, location, and
object classifier estimates, respectively. The
blue, red and green dots correspond to the face,
location, and object recalls made by the subject
... shifted forward by three time points to
account for lag to the peak hemodynamic response
...
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Mean over 9 subjects
fMRI recorded every 1.8 sec (1 scan).
Fig. 2. Event-related average of the classifier's
estimates of contextual reinstatement for the
time intervals surrounding recall events... The
dotted line at t 0 represents the scan on which
the verbal recall was made. ... The three plots
have not been shifted to account for hemodynamic
lag effects... points marked with stars and
circle differ at P lt 0.01 and P lt 0.05,
respectively.
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fMRI recorded every 1.8 sec (1 scan).
Fig. 2. Event-related average of the classifier's
estimates of contextual reinstatement for the
time intervals surrounding recall events... The
dotted line at t 0 represents the scan on which
the verbal recall was made. ... The three plots
have not been shifted to account for hemodynamic
lag effects... points marked with stars and
circle differ at P lt 0.01 and P lt 0.05,
respectively.
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fMRI recorded every 1.8 sec (1 scan).
Neuronal activity occurred 1 scan (1.8 sec) ...
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fMRI recorded every 1.8 sec (1 scan).
Neuronal activity occurred 2 scans (3.6 sec) ...
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fMRI recorded every 1.8 sec (1 scan).
Neuronal activity occurred 3 scans (5.4 sec)
before the BOLD signal.
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fMRI recorded every 1.8 sec (1 scan).
The pattern started to differ from baseline
already 6 scans (10.8 sec) before verbal recall.