Project 2: Neural Basis of Emotion-Reason Interactions
We are also probing the relationship between rational and emotional processing.
Much neuropsychological data implicates VMPFC in emotional processing (Damasio,
1997; Goel & Dolan, 2001a; Harlow, 1868; Lane, Reiman, Ahern, Schwartz,
& Davidson, 1997; Pietrini, Guazzelli, Basso, Jaffe, & Grafman, 2000)
and the L/DLPFC in high-level cognitive processing (Drewe, 1974; Goel, Grafman,
Tajik, Gana, & Danto, 1997; Goldman-Rakic, 1987; Rowe, Owen, Johnsrude,
& Passingham, 2001; Shallice, 1988; Stuss et al., in press), including
logical reasoning (Goel et al., 2000; Goel & Dolan, 2001b; Goel &
Dolan, in press-a; Goel, Gold et al., 1997; Goel et al., 1998; Houde et al.,
2001; Knauff, Mulack, Kassubek, Salih, & Greenlee, in press; Parsons &
Osherson, 2001). However, with a few exceptions (Gray, Braver, & Raichle,
2002), the literatures on cognition and emotion are largely independent of
each other. It has been observed that some patients with VMPFC lesions, in
addition to having significant emotional and social problems, make poor decisions
(Anderson, Damasio, Tranel, & Damasio, 2000). This has led to the suggestion
that there is a causal connection between emotional deficits and poor decision
making (Bechara, Damasio, & Damasio, 2000; Damasio, 1996). One possible
basis for this connection is an interaction between L/DLPFC and VMPFC during
reasoning. While several neuroimaging and patient studies have shown a dissociation
between L/DLPFC and VMPFC in cognitive and affect processing (Goel & Dolan,
2001a; Greene, Sommerville, Nystrom, Darley, & Cohen, 2001; Hariri, Bookheimer,
& Mazziotta, 2000; Koechlin, Corrado, Pietrini, & Grafman, 2000; Stuss
& Levine, in press), very little is known about the functional interaction
between the two regions.
We are currently undertaking a series of fMRI studies in which
normal controls are confronted with a conflict between rational and emotional
responses within the domain of deductive and inductive reasoning. In one recent
study we explored the interaction between belief and reason. We have shown
(Goel & Dolan, 2003) that within the context of reasoning involving inhibitory
or misleading beliefs, the crucial element in the modulation of reasoning
by beliefs is the preferential engagement of VMPFC. Where the VMPFC is preferentially
engaged, subjects are more likely to generate responses based upon their belief-biases.
This contrasts with correct logical reasoning that requires relatively greater
activation of L/DLPRC. The involvement of VMPFC and its strong associations
with affective processing indicates that belief-bias effects on reasoning
may be a special instance of the modulatory effect of emotion on cognition
(Damasio, 1994). The fact that the response of the VMPFC is specific to inhibitory
belief trials and is deactivated (with respect to facilitory belief trials)
during correct inhibitory belief trials (while L/DLPFC is activated) suggests
a reciprocal relationship between VMPFC and L/DLPFC.
To further explore this relationship we (Goel & Dolan, in
press-b), scanned normal subjects using event-related fMRI, while they engaged
in identical logical reasoning tasks that varied only in emotional saliency
(e.g. Some Canadians are not children; All Canadians are people; Some people
are not children. vs. Some wars are not unjustified; All wars involve raping
of women; Some raping of women is not unjustified). Despite identical logical
form and content categories across emotionally salient and neutral reasoning
conditions, lateral and ventral medial prefrontal cortex showed reciprocal
response patterns as a function of content saliency. Neutral reasoning trials
resulted in enhanced activity in L/DLPFC and suppression of activity in VMPFC.
By contrast, salient reasoning trials resulted in enhanced activation in VMPFC
and suppression of activation in L/DLPFC. This reciprocal engagement of L/DLPFC
and VMPFC provides evidence for a dynamic neural system for reasoning, the
configuration of which is strongly influenced by emotional saliency and leads
us to the following hypothesis:
H2. The interaction between rational and emotional processing is underwritten by reciprocal neural activation in L/DLPFC and VMPFC,
We are now expanding the scope of this project. In particular, we are interested in the fact that emotions can be introduced into the decision-making process in at least 3 ways: (i) in the content/substance of the reasoning task (as in the above study); (ii) in the presentation of the content of the reasoning task (i.e. context); and (iii) in the preexisting mood of the subject. Given this, we want to focus on two questions: (a) Do these three manipulations engage the same neural systems? (b) How does content/substance of reasoning interact with context (e.g. voice intonation) and subject mood.
Basic operating funds for this study are covered by my NSERC grants (Title of Project: Neurology of Belief & Logic) and Premier’s Research Excellence Award (Title of Project: Neurobiology of Rationality).
Nov. 10, 2003