• What makes somatosensation so different from other senses to look exclusively into the impact of attention onto that sensory system?
Somatosensory Cortex• Areas 1, 2, and 3, which constitute PRIMARY SOMATOSENSORY AREA I, 40 is SECONDARY SOMATOSENSORY AREA II and areas 5 and 7, which constitute the SOMATOSENSORY ASSOCIATION AREA.
SEP• Somatosensory evoked potentials • By combining SEP recordings at different levels of the somatosensory pathways, it is possible to assess the transmission of the afferent volley from the periphery up to the cortex.
• latency of 38 and 68ms• attentional modulation of SEFs (125 and 138ms)• one such variable might be the level to what extend stimuli have to be processed in order to perform a particular task.
• SEP consists of the components P50, N70, P100, N140 and positive late component(LC).• spatial attention alters the neural responses to transient stimuli is not a hard-wired mechanism but might be inﬂuenced by a number of variables.
• Spatial separation of stimulation sites as well as inter stimulus intervals play an important role to determine which component of the SEP is modulated with attention.• The somatosensory system in particular seems to be organized in a way to automatically shift attention to that body location where something happens.
• When you search for key-ring in a dark bag, spatial and non-spatial information gathered from your sense of touch highly determines the success of this search.
ERP• ERP(Event Related Potential) • measured brain response that is directly the result of a thought or perception. • measured with EEG, MEG
SSSEP• Somatosensory Steady-Stated Evoked Potentials• A form of response to repetitive sensory stimulation in which the constituent frequency components of the response remain constant with time in both amplitude and phase• 20 (left ﬁnger), 26 Hz (right ﬁnger)• Amplitude was increased with attention
The Neuronal Basis of Preferential Stimulus Processing• A sensory gain control mechanism : visual modality • Ampliﬁcation / Suppression • Attended or not stimulus• A change in the temporal pattern of action potentials
Synchronisation of neuronal responses• Correlation between pairs of neurons in SII• Temporal synchronisation of action potentials of neurons that code the to-be- attended stimulus produces a ‘pop-out’ from the background noise.