Commentary: Viewing photos and reading nouns of natural graspable objects similarly modulate motor responses

Citation: Makris S (2015) Commentary: Viewing photos and reading nouns of natural graspable objects similarly modulate motor responses. Marino et al. (2014) in their paper (Frontiers in Human Neuroscience) have tried to investigate how the semantic processing of graspable objects involves an activation of the motor cortex in line with the affordance hypothesis originally proposed by Gibson (1979). They devised a go/non-go behavioral task, during which they presented photos or nouns of natural graspable and non-graspable objects, while for some of the trials the stimuli viewed were scrambled images of the same objects or pseudowords. Participants viewed the stimuli for a period of 150 ms, after which they had to respond to a go or non-go signal (whether the stimuli were real or not) as part of a semantic task. They found that subjects' responses were slower when they were viewing the photos or reading the nouns of graspable objects, as compared to non-graspable ones. The authors explained that this delay in motor responses following the images or nouns of graspable objects is a proof of the motor cortex involvement in the semantic processing of objects that afford a motoric action. Even though these findings are in line with some previous reports about an early activation and involvement of the motor system in language and semantic processes (Pulvermueller et al., 2001, 2005), in this commentary we argue that the stimulus onset asynchrony (SOA) of 150 ms is too early for an affordance effect to occur and thus, we will try to provide a different account of their results and leave some room for further insight on the topic. There is mounting research evidence suggesting that the simple viewing of objects with action significance can stimulate the motor cortex into generating appropriate motor plans, even in cases that there is no action intention This is the theory of affordances as originally described by Gibson (1979). Within the affordance literature a key aspect for investigation has been the temporal evolution of the affordance effect. Ellis and Tucker (2000) in a series of behavioral investigations have suggested that the affordance effect is slow and gradually develops 500 ms after the stimulus onset. On the other hand, in previous research with TMS we have proved by means of measures of corticospinal excitability (motor evoked potentials) that the affordance effect is present at 300 ms and rapidly dissipates 500 ms after the stimulus onset (Makris …