Davidson, R.J. (2004)
What does the prefrontal cortex "do" in affact:
perspectives on frontal EEG asymmetry research
Biological Psychology, 67, 157-182, 219-233
Historical appraisal alpha asymmetry and emotion
1979 EEG
asymmetry first reported, at that time p 220 ' research on CNC substrates of
emotional processes largely restricted to non-human species with focus on the
subcortical'
But p222
we now know that ' Emotion and
motivation are instantiated in complex circuitry involving both cortical and sub
cortical components'
Work
presented up to 2004 has evolved with little connection to this recent core neuroscience on structure and
function - D argues that this state of affairs must change therefore D
specifies some questions.
What is the PFC doing in emotion?
some
facts to bear in mind
•
PFC
is heterogenous (anatomically and functionally) and part of a larger network
•
Based
on cell recordings- animal studies ( 2
macaque monkeys) ' tasks that include a response component will be more likely
to show affect related PFC activation asymmetry in the dorsal lateral regions
and it is activity in these regions that is most likely to be reflected in
scalp recorded brain signals'
•
Recent
studies ' have also identified a ventromedial region of PFC that shows robust
asymmetries during response inhibition tasks' ( also patient data with damage
on right side I.e. r. VmQPFC ? Particularly susceptible to punishment)
p223
•
Suggestions
that regions of the l.PFC play an important role in inhibiting the amygdala -'
strong inverse relations between activation in the l.v.m.PFC and amygdala when
subjects are asked to voluntarily down regulate
their negative affect. The findings collectively imply that what the PFC
is doing in emotion is clearly NOT mediating emotional responses but rather
moderating patterns of activity in other parts that control the primary
emotional response'
'Unfortunately
though, little work at the human level has begun to parse emotion in a fashion
that derives from and honours the distinctions that are made at a neural level'
' For
certain types of emotional processes the presence of a particular pattern of
functional prefrontal asymmetry may be necessary
but not sufficient for the emotional
state in question, or may simply be contributory'
KRO -
moderation ? emotional tone
Self
report of conscious mood - a summary index of a range of complex emotional
processes
IDs in baseline activations
p225 '
individuals with higher levels of l.sided PQF activity do indeed have a more
positive profile of peripheral biological indicators' there is evidence of well
being , the ability to cope with a negative event (resilience).
Reward is
a factor that has been manipulated
P
225 ' it is during the period in
anticipation of reward that the most pronounced l. Frontal activation is
observed'
p226
Damasio
v.m.PFC ' crucial substrate for affect guided decision making' - ? are there
functional asymmetries Note Davidson has argued that there are functional
asymmetries in dorsal prefrontal
P227
SES and
asymmetry
Tomarken
( this issue) ' relations between SES and PF asymmetry in adolescence. The
lower the SES, the greater the relative right-sided prefrontal activity'
Empirical and methodological issues
p221 '
the PF sector most directly associated with emotion is the sector that is least
likely to be reflected in scalp-recorded brain electrical signals' hence the
importance of a neurally informed strategy'
KRO - from clinical practice we
know that it would be naive to expect more than a generalised view of the
activation patterns that underlying each electrode
Harmon-Jones
( this issue) Variations in levels of anger lead to increased left-frontal
activation and ultimately approach behaviours. Davidson's caveat -' but only if
there are response options that allow the individual to overcome whatever is
thwarting the goal'
p227
articles ' establish prefrontal EEG asymmetry measures as reflecting, at least
in part, trait like variations in brain function that appear to predict
interesting and important features of affective style'
Reference
electrode some studies report that method robust to location, some do not.
Important to take into account that EEG recordings reflect the potential
difference between two locations and there is no electrically neutral location
anywhere on the body
other
frequency bands
Oakes et
al, 2004 ' although alpha shows the predicted inverse relation with metabolism
' ' the frequency band most consistently and strongly associated with glucose
metabolism was gamma'
Pizzagalli
refs for comparisons between frequency bands
