The development of sub-disciplines within cognitive neuroscience follows common sense categories such as language, audition, action, memory, emotion and perception among others. There are also well-established research programmes into temporal perception, spatial perception and mathematical cognition that also reflect the subjective impression of how experience is constructed. There is of course no reason why the brain should respect these common sense, text book divisions and, here, we discuss the contention that generalized magnitude processing is a more accurate conceptual description of how the brain deals with information about time, space, number and other dimensions. The roots of the case for linking magnitudes are based on the use to which magnitude information is put (action), the way in which we learn about magnitudes (ontogeny), shared properties and locations of magnitude processing neurons, the effects of brain lesions and behavioural interference studies. Here, we assess this idea in the context of a theory of magnitude, which proposed common processing mechanisms of time, space, number and other dimensions.

Pain is intimately linked with action systems that are involved in observational learning and imitation. Motor responses to one's own pain allow freezing or escape reactions and ultimately survival. Here we show that similar motor responses occur as a result of observation of painful events in others. We used transcranial magnetic stimulation to record changes in corticospinal motor representations of hand muscles of individuals observing needles penetrating hands or feet of a human model or noncorporeal objects. We found a reduction in amplitude of motor-evoked potentials that was specific to the muscle that subjects observed being pricked. This inhibition correlated with the observer's subjective rating of the sensory qualities of the pain attributed to the model and with sensory, but not emotional, state or trait empathy measures. The empathic inference about the sensory qualities of others' pain and their automatic embodiment in the observer's motor system may be crucial for the social learning of reactions to pain.

The recent upsurge of interest in brain mechanisms of time perception is beginning to converge on some new starting points for investigating this long under studied aspect of our experience. In four experiments, we asked whether disruption of normal activity in human MT/V5 would interfere with temporal discrimination. Although clearly associated with both spatial and motion processing, MT/V5 has not yet been implicated in temporal processes. Following predictions from brain imaging studies that have shown the parietal cortex to be important in human time perception, we also asked whether disruption of either the left or right parietal cortex would interfere with time perception preferentially in the auditory or visual domain. The results show that the right posterior parietal cortex is important for timing of auditory and visual stimuli and that MT/V5 is necessary for timing only of visual events.