A biologically relevant event is normally the source of multiple, typically correlated, sensory inputs. To optimize perception of the outer world, our brain combines the independent sensory measurements into a coherent estimate. However, if sensory information is not readily available for every pertinent sense, the brain tries to acquire additional information via covert/overt orienting behaviors or uses internal knowledge to modulate sensory sensitivity based on prior expectations. Cross-modal functional modulation of low-level auditory areas due to visual input has been often described; however, less is known about auditory modulations of primary visual cortex. Here, based on some recent evidence, we propose that an unexpected auditory signal could trigger a reflexive overt orienting response towards its source and concomitantly increase the primary visual cortex sensitivity at the locations where the object is expected to enter the visual field. To this end, we propose that three major functionally specific pathways are employed in parallel. A stream orchestrated by the superior colliculus is responsible for the overt orienting behavior, while direct and indirect (via higher-level areas) projections from A1 to V1 respectively enhance spatiotemporal sensitivity and facilitate object detectability.
Laminar distribution of neurons in extrastriate areas projecting to visual areas V1 and V4 correlates with the hierarchical rank and indicates the operation of a distance rule,
BologniniN.SennaI.MaravitaA.Pascual-LeoneA.MerabetL. B. (2010).
Auditory enhancement of visual phosphene perception: the effect of temporal and spatial factors and of stimulus intensity,
GhazanfarA. A.ChandrasekaranC.LogothetisN. K. (2008).
Interactions between the superior temporal sulcus and auditory cortex mediate dynamic face/voice integration in rhesus monkeys,
OliverD. L.BeckiusG. E.BishopD. C.LoftusW. C.BatraR. (2003).
Topography of interaural temporal disparity coding in projections of medial superior olive to inferior colliculus,
PosnerM. I.NissenM. J.OgdenW. C. (1978).
Attended and unattended processing modes: the role of set for spatial location, in:
Modes of Perceiving and Processing Information,
PickH.SaltzmannE. (Eds), pp.
137–157. John Wiley and Sons Inc., Hillsdale, NJ, USA.
RomeiV.MurrayM. M.MerabetL. B.ThutG. (2007).
Occipital transcranial magnetic stimulation has opposing effects on visual and auditory stimulus detection: implications for multisensory interactions,