Neuroimaging and neuropsychological experiments suggest that modality-
preferential cortices, including motor- and somatosensory areas, contribute to
the semantic processing of action related concrete words. Still, a possible
role of sensorimotor areas in processing abstract meaning remains under
debate. Recent fMRI studies indicate an involvement of the left sensorimotor
cortex in the processing of abstract-emotional words (e.g., “love”) which
resembles activation patterns seen for action words. But are the activated
areas indeed necessary for processing action-related and abstract words? The
current study now investigates word processing in two patients suffering from
focal brain lesion in the left frontocentral motor system. A speeded Lexical
Decision Task on meticulously matched word groups showed that the recognition
of nouns from different semantic categories – related to food, animals, tools,
and abstract-emotional concepts – was differentially affected. Whereas patient
HS with a lesion in dorsolateral central sensorimotor systems next to the hand
area showed a category-specific deficit in recognizing tool words, patient CA
suffering from lesion centered in the left supplementary motor area was
primarily impaired in abstract-emotional word processing. These results point
to a causal role of the motor cortex in the semantic processing of both
action-related object concepts and abstract-emotional concepts and therefore
suggest that the motor areas previously found active in action-related and
abstract word processing can serve a meaning-specific necessary role in word
recognition. The category-specific nature of the observed dissociations is
difficult to reconcile with the idea that sensorimotor systems are somehow
peripheral or ‘epiphenomenal’ to meaning and concept processing. Rather, our
results are consistent with the claim that cognition is grounded in action and
perception and based on distributed action perception circuits reaching into
modality-preferential cortex