The mind provides a functional matrix or context in which external stimuli are received, evaluated and are the subject of responses. In the case of anxiety responses, these are physically manifested in the release of hormones such as adrenalin and cortisol. Under normal circumstances, the ideal is that these hormones should only be released in appropriate quantities and at appropriate times and hence that the system that regulates them should tend towards stability and should avoid excessive sensitivity or, indeed, insensitivity. The specific context in which this normally takes place has an inbuilt drive towards stability and levels of response are therefore tailored towards this end. In my view, this system operates differently in autistic and neurotypical brains.
I propose that the operation of this system takes place by a process of mediation through feedback. The nature of this feedback is key and, to clarify it’s operation, I suggest two analogies:
Feedback is a commonly experienced issue in PA systems. In such systems sound is picked up by a microphone and electronically amplified before being reproduced at higher amplitude by a loudspeaker. This process works well as long as the overall sensitivity of the system does not exceed a certain value (determined by, inter alia, the acoustic properties of the environment in which the system is operating). If the overall system gain exceeds this level, positive feedback will occur: a small sound will be picked up, amplified and reproduced but the amplitude of the reproduced sound will be such that the microphone will pick up part of the reproduced sound which will then be further amplified, picked up again and yet further amplified leading to a runaway chain reaction and resulting in the familiar howl of audio feedback. This is positive feedback at work.
In the early days of steam engines there was a substantial risk that the engine would run wild and cause damage or injury. To avoid this, the mechanical governor was devised. Two weights were attached to a shaft such that they could move in and out perpendicular to a rotating shaft driven by the engine. Just as a dancer can control the speed of a pirouette by allowing their arms to stretch out or retract, the weights of the governor will tend to fly out in relation to the speed of rotation. As the weights of the governor fly further out, they act upon the steam inlet valve, closing it down and slowing the engine. The weights then retract, allowing the valve to open again and speed the engine up again. After a period of “hunting” a stable balance is reached. The greater the speed, the more the governor will tend to shut down the steam supply. This is negative feedback at work.
My suggestion is that, in the brain, a potentially stressful stimulus will lead to an anxiety response that should be broadly proportionate to the perceived threat. This in turn leads to similarly proportionate release of stress hormones. Since the brain normally tends towards stability, this circular process will have neutral or negative feedback – successive stimuli will gradually lead to a tapering off of response. Subsequent similar stimuli will tend to produce a reduced response as the system reevaluates the actuality of the threat. If the threat does not result in actual harm, this will further reduce the intensity of response and the whole system will gradually adjust to a state of substantially reduced sensitivity, reverting to a resting state of homeostasis and producing little in the way of anxiety responses to further stimuli of similar nature – successive shocks have a diminishing effect, the system gain is turned down.
Anecdotally, it seems likely that the autistic brain responds more sensitively to a given stimulus than does the neurotypical. Taken as a whole, it is a more sensitive system and one that is more readily perturbed – autistic subjects are known to cope poorly with change and extremes of stimulation – and such inputs have the effect of pushing the system further from a stable state. I suggest that the processing matrix of the autistic brain does not so readily achieve or maintain homeostasis – by it’s very nature, it operates further away from the conventional stable state and hence a similar initial stimulus may produce a response that is quantitatively similar to or perhaps greater than that of the neurotypical brain. However, given the different initial value, the outcome will be yet further away from stability. The vital difference that brings this higher sensitivity into being is that the feedback loop now has positive gain such that the initial response renders the system more, rather than less, sensitive. In consequence, the impact of subsequent stimuli will be greater. The net gain of the system is thus further increased and this response continues a runaway escalation, driving the system ever further from homeostasis.
While not in any sense a proof, the validity of this model is supported by the observed responses of autistic subjects to noise and strong visual, emotional, social and cognitive inputs. The autistic subject may be aware of the disproportionate nature of his or her responses and this awareness may be a further precipitating factor which drives their responses ever further from the “ideal” of homeostasis and towards states of severe anxiety. Anxiety may cause symptoms which, in turn create further anxiety. The autistic subject therefore experiences a double whammy – a more sensitive system and a tendency towards positive feedback
It follows from this that intervention with conventional anxiolytics is likely to be of limited efficacy since they only address the final outcome i.e. the production and impact of hormones, whereas the “problem” is actually an inherent property of the overall system and, as such, appears to be less – if at all – subject to simple chemical adjustment such as is offered by clinical anxiolytics.