The Mind-Body Problem and Current
Behavioural-Neuroscience on Fear-Conditioning
João Fonseca
Instituto de Filosofia da Linguagem
Universidade Nova de Lisboa
What is the Mind-Body Problem?
There are several technical ways of presenting and defining the Mind-Body Problem
For the present purposes the more or less prosaic distinction between Subjective and Objective
is enough.
Two distinct Domains: Objective/Body and Subjective/Mind
1- Objective: Intersubjective measurable data.
Body- External objects (not just our organic body – from Quarks to Galaxies) and the physical principles
(laws) that govern them.
It is the domain of Physics and the other natural sciences (including Neuroscience whose
external/physical object of research is the Brain)
2- Subjective: Private experiences
Mind- Thoughts, Sensations, Feelings
It is the domain of Introspection, Certain branches of Psychology, Phenomenology, and Philosophy
So, What is the ‘Problem’ in the Mind-Body Problem?
Assuming these two radically distinct domains (Mind/Subjective and Body/Objective) what
is the relation between the two?
For instance, the neuroscientist Joseph LeDoux states that:
«the mind-body problem, the problem of how consciousness comes out of brains, [is]
arguably the most difficult problem there is and ever was.» (1998, 268)
This quotation can take us to a nice and smooth transition to the the question of how this
problem is reflected in current neuroscientific practice.
Joseph LeDoux and Fear Conditioning
LeDoux innovative proposals and empirical findings on the subject of Fear Conditioning are
today the mainstream paradigm used by hundreds (if not thousands…) of the neuroscience
community working on this field across the globe
But LeDoux’s scientific achievements are built assuming explicitly a philosophical concern: the
dificulty/impossibility of explaining subjective experiences by scientific/objective means (the MindBody Problem).
For LeDoux, scientific research on emotions (including ‘Fear’) should follow a path such that the
mind-body problem is avoided:
«[early emotion researchers] remained focused on subjective emotional experience…[t]his approach
puts the mind-body problem right smack in the middle of the path of progress» (2000)
Accordingly, in respect to the emotion ‘Fear’, something like I like to call ‘LeDoux’s
Principle’ states that: Fear (conditioning) can and should be studied only by taking into
consideration the unconscious brain mechanisms underlying that process:
«I find it neither necessary nor desirable to insert a conscious state of fear into the chain
of events connecting trigger stimuli to fear responses» (1998)
Note that (and this is very important), LeDoux’s principle is not claiming that because
of the mind-body problem there is a part of the process of fear-conditioning we have to
left behind. Instead he is asserting that fear/fear-conditioning has nothing to do with
subjective feelings and, therefore, we can investigate fear without facing the mind-body
problem. For this reason, Fear Conditioning studies are complete, we have all necessary
data.
LeDoux’s line of reasoning presuppose the Mind-Body Problem (and the prior and related
Mind-Body distinction) as such.
But, is the Mind-Body Problem/Distinction well sustained?
My claim is that it is not. This claim is sustained by somewhat complex and technical
philosophical arguments that, for obvious reasons, I cannot address here.
So, I suggest a different track: deny the Mind-Body Problem/Distinction and evaluate the
consequences! My claim here will be that, regarding Fear Conditioning research, the consequences
of denying the Mind-Body Problem consists on an enlargement of evidence.
Return to Fear Conditioning research
LeDoux experiments and results deal mostly with Classical Fear conditioning – US/CS pairing: reflex
conditioned behavioral response (eg Freezing)
Instrumental/Operant Fear Conditioning – The acquisition of an active avoidance behavior that
suppresses the outcome of (noxious) US via the presentation of a CS eg: Pressing a lever in order to
avoid/suppress the upcoming shock, or escape behaviors.
It seems not to exist an intense research on Instrumental Fear Conditioning in Current Neuroscience
Killcross et al voice this perplexity:
«The role of [amygdaloid nuclei] in alternative indices of fear conditioning, including the instrumental
choice responses involved in avoidance or conflict behavior, is much less clear [than reflex, pavolovian
induced, responses such as freezing]» (1998)
LeDoux says the following (in the “Amygdala” article from Scholarpedia):
« In the 1980s, researchers began to use tasks that isolated the Pavlovian from the instrumental components
of the task to study the brain mechanisms of fear. This strategy allowed a focus on the fear reaction
conditioned by the shock rather than on behaviors that avoid the shock.» (He seems to consider this as an
achievement or progress)
LeDoux’s assumption is that the relevant brain mechanisms for Classical and Instrumental Fear
Conditioning are exhausted by the former. Therefore, an exhaustive study of the neural basis of
instrumental fear condition would be explanatory redundant in relation to classical conditioning.
But, against LeDoux’s assumption there is some cumulative empirical evidence that suggest
a double dissociation between the structures responsible for Classical Fear Conditioning
and Instrumental one.
In particular, several independent experiments show that the Classical Fear Conditioning
neural pathway (lateral amygdala (LA) – central amygdala (CA)) is functional independent
from the Instrumental one (basolateral amygdala (BLA)). Killcross et al 1997 ;
Amorapanth, LeDoux & Nader, 2000 ; and others
So, lets assume that Instrumental Fear Conditioning has a autonomous research path from
Classical Conditioning after all.
So, lets focus on Instrumental Fear Conditioning.
If, according to some data (BLA – non declarative; Portavela et al, 2004, 2005), in Instrumental Fear
Conditioning experimental settings, creatures do not rely on Declarative Memory in order to anticipate the
US by the presentation of CS, what drives them to avoid the supposedly neutral CS?
By dismissing the Mind-Body Problem/Distinction we are allowed to suppose the following ‘Crazy
Hypothesis’: Maybe the Feeling of Fear is what drives them! – Their non-declarative associative memory
pairs the CS with their subjective feeling of fear (the CS itself becomes noxious)
We are able to formulate this hypothesis by allowing our own subjective experiences to be part of the
available data and by noticing (by introspection) the similarities between our behaviors elicited/caused by
our felling of fear and those behaviors being measured in Instrumental Fear Conditioning protocols (with
animals). We can even suggest the following causal profile definition to the Feeling of Fear:
Feeling of Fear causes active, non-stereotyped, non-reflexive (voluntary) avoidance behaviors (from the
CS)
This causal profile of the Feeling of Fear can assume an important explanatory role in Instrumental Fear
Conditioning research.
WARNING: This is just an initial working hypothesis. What follows is a simple hypothetical sketch
of how this admission of the hypothesis can have an impact on empirical research. No serious
scientific results are suggested!!
1st Empirical claim:
If the Feeling of Fear has such a relevant causal property – with obvious survival advantages, then, [and
contrarily to LeDoux’s suggestion (DLPFC)] the correlated neural structure must be a evolutionary very old
one.
Answer
The dorsal Peraqueductal Gray (dPAG) is a very old evolutionary structure situated in the midbrain (part of
the Brainstem in humans) is known for modulating fear and/or fear reactions
1- Human subjects report strong subjective feelings of fear, terror and desire to escape (similar to
symptoms associated to panic attacks) during the electrical stimulation of their dPAG. Alternatively, it has
been reported that spontaneous panic attacks activates this structure (interestingly, the cortex does not play
any role on these more extremes cases of Feeling of Fear in humans – contradicting LeDoux’s assumption
in the contrary).
2- In animals/mice, electrical stimulation of the dPAG elicits strong active avoidance behavior, including
escape, running, alertness and even instrumental behavior like pressing a lever in order to stop the electrical
stimulation.
3- The dPAG is present across species (vertebrates – not only mammals) and with similar functional
properties (non-dependent on the existence of a cortex!).
2nd Empirical Claim
If, taking into consideration the evidence stating that:
1- the BLA is critically involved in ‘Instrumental Fear Conditioning’ and
2- there is a correlation between the dPAG and the Feeling of Fear,
then, according to the hypothesis tha the ‘Feeling of Fear’ has a causal-explanatory role on
Instrumental Fear conditioning, some sort of structural connection between BLA and dPAG is
required.
Answer
Here again, a lot of recent empirical results stress the existence of direct (bi-directional)
pathways between the BLA and dPAG. In particular, these body of research shows that the
BLA is responsible for the menemonic (conditioning) aspect whereas the dPAG is responsible
for the emotional processing and responses, eg: Brandão et al, 2008; Oliveira et al, 2004;
Zanoveli, 2008.
3rd Empirical Claim
Taking into consideration the Feeling of Fear causal profile [(Feeling of Fear causes active,
non-stereotyped, non-reflexive (voluntary) avoidance behaviors (from the CS)], the correlated
neural structure (the dPAG) should not establish direct pathways with pre-specified reflexive
motor outputs. This can suggest evidence for a non-deterministic causal role of a noxious
feeling (Fear) the animal avoids by adopting the most adequate behavioral strategy in a certain
environmental/situational condition.
Answer
In fact, recent studies strongly suggest that dPAG satisfies this condition. On this respect,
Brandão et al states that: «[W]hereas the vPAG is involved in the motor aspects of freezing
response through descending projections to the spinal cord, the dPAG activates this defensive
posture through ascending projections to rostral structures» (2008, 7)
I.e., whereas the vPAG establishes downward projections to motor responses, the dPAG does
not and influences upstream decision-making structures (like the superior colliculus)
So, (some sort of) concluding
Denying the Mind-Body Problem/Distinction allows us to mesh traditional ‘subjective’ and
‘objective’ data. More particularly, we are able to suggest a causal profile for the ‘Feeling of
Fear’, thus enabling it to be part of the ‘objective’ structure of the world.
As a practical consequence it was shown that a greater explanatory power is gained if
compared with LeDoux research paradigm which is almost mute regarding Instrumental Fear
Conditioning . This suggests an unification of several disperse and scattered data from
different and unrelated sources from contemporary neuroscience into a single explanatory
scheme of ‘Instrumental Fear Conditioning’)
I hope I have shown how the current formulation of the Mind-Body problem is constraining
contemporary research on Fear-Conditioning. The adoption of Mind-Body
Problem/Distinction can act as a dogma and stagnate scientific progress.
We have, therefore, good pragmatic reasons to abandon the Mind-Body Problem/Distinction