Exaggerated object affordance and absent automatic inhibition in alien hand syndrome

Abstract

Patients with alien hand syndrome (AHS) experience making apparently deliberate and purposeful movements with their hand against their will. However, the mechanisms contributing to these involuntary actions remain poorly understood. Here, we describe two experimental investigations in a patient with corticobasal syndrome (CBS) with alien hand behaviour in her right hand. First, we show that responses with the alien hand are made significantly more quickly to images of objects which afford an action with that hand compared to objects which afford an action with the unaffected hand. This finding suggests that involuntary grasping behaviours in AHS might be due to exaggerated, automatic motor activation evoked by objects which afford actions with that limb. Second, using a backwards masked priming task, we found normal automatic inhibition of primed responses in the patient's unaffected hand, but importantly there was no evidence of such suppression in the alien limb. Taken together, these findings suggest that grasping behaviours in AHS may result from exaggerated object affordance effects, which might potentially arise from disrupted inhibition of automatically evoked responses.

Continuous force measurements reveal no inhibitory control deficits in Parkinson’s disease

“…The force response analysis used here was built upon previous work by McBride et al (2012McBride et al ( , 2013McBride et al ( , 2018, and specifically adapted to be suitable for PwP. The data from the PwP had a lower signal-to-noise ratio than data from the HCs due to many PwP exhibiting the tremor that is often associated with their disease.…”

“…An alternative method of response measurement, therefore, is to directly measure response force. Indeed, such measures have been used successfully to measure simultaneous activation of competing motor plans, inhibition, and control in healthy adult participants (McBride et al 2012(McBride et al , 2018 as well as neurological patients (McBride et al 2013), and similar measures have provided important constraints on computational models of human behaviour (Servant et al 2015).…”

Continuous force measurements reveal no inhibitory control deficits in Parkinson’s disease

“…The force response analysis used here was built upon previous work by McBride et al (2012McBride et al ( , 2013McBride et al ( , 2018, and specifically adapted to be suitable for PwP. The data from the PwP had a lower signal-to-noise ratio than data from the HCs due to many PwP exhibiting the tremor that is often associated with their disease.…”

“…An alternative method of response measurement, therefore, is to directly measure response force. Indeed, such measures have been used successfully to measure simultaneous activation of competing motor plans, inhibition, and control in healthy adult participants (McBride, Sumner, & Husain, 2012 as well as neurological patients (McBride, Sumner, Jackson, Bajaj, & Husain, 2013), and similar measures have provided important constraints on computational models of human behaviour (Servant, White, Montagnini, & Burle, 2015).…”

Choosing to Stop: Responses Evoked by Externally Triggered and Internally Generated Inhibition Identify a Neural Mechanism of Will

“…The presence of a glass on the table compels them to drink, even when they are not thirsty. In the dramatic example of unilateral "anarchic hand" (Kritikos, Breen, & Mattingley, 2005;Della Sala, Marchetti, & Spinnler, 1991), the unsuppressed stimulus-driven actions of the affected hand interfere with their ability to achieve voluntary action goals with the unaffected hand (McBride, Sumner, Jackson, Bajaj, & Husain, 2013).…”