Ventral Intraparietal (VIP)

 

Nomenclature, Location, Function, Connectivity, Human Homologue, Glossary

 

 

Nomenclature:

 

    VIP has also been defined as part of area Intraparietal dorsal (IPd) which spanned almost the entire rostral-caudal length of the IPS.

Location:

Gross Anatomical Location

    VIP is located in about the middle third of fundus of the Intraparietal Sulcus (IPS).  At its maximum extent it spans ~ 5 mm mediolaterally and ~ 8 mm rostrocaudally, beginning anterior to the annactent gyrus and extending up onto both the medial and lateral sulcal walls. [3]

 

Architectonic and Cytoarchitectonic Definition

    Architectonics for VIP have been mainly myelination studies ([1], [3], [5], [4], [6]), along with recent immunoreactivity studies, [1].  Previous to [1], VIP had been archetechtonically identified as the lightly myelinated region in the fundus.  However, [1] claim that VIP is not sufficiently homogeneous in myelination, or immunoreactivity to be identified as one continuous area.  They suggest that VIP be broken up into VIPm (medial), which has a band of high myelination in layers 3 through 5, and VIPl (lateral) which is the lightly myelinated deep fundal region.

Function/Physiological Delineation:

    Mostly due to [3], [4], and [7] VIP is distinguished from surrounding areas on the basis of its response properties  First we enumerate the types of cell responses that have been found in VIP:

    * Unimodal cells that respond to speed and direction of a moving visual stimulus.

    * Unimodal cells that respond only to visual stimuli very near to the face. (Near cells)

    * Bimodal cells that respond to visual and tactile stimuli:

        -- Cells whose visual and tactile receptive fields match in size and location and direction sensitivity.  For example, a cell that responds to a peripheral visual stimulus in the upper left quadrant of the head and face.

        -- Cells that respond to visual stimuli moving toward the tactile receptive field region. (Independent of gaze.) (Trajectory Cells)

    * Cells that respond to vestibular stimulation (head motion).

 

    Cell response notes from [3]: In one sample of 88 neurons, 80% showed a preferred direction (responded twice as well to a stimulus moving in the preferred direction compared with a stimulus moving in the null direction).  Many neurons were also selective for speed of stimulus motion.  The degree of speed tuning was on average twice as broad as that reported for MT.

 

    To locate the borders of VIP, [3] recorded from 107 neurons in 5 hemispheres in 3 rhesus monkeys.  Since the middle part of the medial wall of the sulcus has cells with no visual activity, the medial border of VIP was identified by finding the first direction selective visual responsive cells.  Its lateral border was also delineated in this way since the next most lateral area is Lateral Intraparietal (LIP) which is not direction selective.  Caudally, the visually responsive cells of VIP give way to purely somatosensory cells in the fundus.  Rostrally, motion and direction sensitive cells give way to cells that respond visually but are not direction or motion sensitive.

 

Connectivity:

 

Outputs

    VIP projects to an area of premotor cortex known as F4.  This region contributes to head and mouth movements.  This region also has cells that respond similarly to cells in VIP, i.e. trajectory neurons, bimodal neurons and near neurons.

 

Inputs

    Mostly due to a series of detailed retrograde tracer experiments by [1].  Connections were said to be strong, medium, and light according to this scale:

    Strong: 20 or more stained cells per mm2  Moderate: ~ 12-20 stained cells per mm2  Light: ~ 2-12 stained cells per mm2.

 

The connections grouped physiologically:

 

* Somatosensory :

    -- Area 5 (ventral) (5v) Moderate-Strong

    -- Operculator Area 7 (7op) Light-Moderate

    -- Somatosensory Area 2 (2) Light

 

* Visual :

    -- Ventral Lateral Intraparietal (LIPv) Strong

    -- Dorsal Lateral Intraparietal (LIPd) Light-Moderate

    -- Parietal-Occipital (PO) Light-Moderate

    -- Lateral Occipital Parietal (LOP) Light-Moderate

    -- Medial Superior Temporal area (dorsal, anterior) (MSTda) Moderate-Strong

    -- Medial Superior Temporal area (dorsal, posterior) (MSTdp) Moderate-Strong

 

 

* Polysensory :

    -- Medial Intraparietal (MIP) Moderate-Strong

    -- Medial Dorsal Parietal (MDP) Moderate-Strong

    -- Somatosensory Area 7b (7b) Light-Strong

    -- Temporal Opercular Caudal (toc) Light-Moderate

    -- Temporal Parietal Occipital (caudal) (TOPc) Light-Strong

    -- Temporal Parietal Occipital (intermediate) (TOPi) Light-Moderate

 

 

 

Fig. 11. Schematic summary of proposed cortical networks involving area VIP. Sulci are labeled and colored gray (buried cortex), and a select set of core architectonic areas (from case B) are indicated. Colored areas, ovals, and text depict regions projecting to VIP, and are coded according to presumed function (see Figure key and text). Multiple colors in LOP, 7b, TPO, 4C depict possible involvement in multiple networks. LOP was partially included in the oculomotor network based on a connectivity study by Schall et al. (1995). Hatched oval in area 24b may be related to a spatial attention network (see text). Bimodal or polymodal areas colored green include 4C (Rizzolatti et al., 1981 a,b; Fogassi et al., 1996), MIP (Colby and Duhamel, 1991), MDP (PEc/PGm of Pandya and Seltzer, 1982), 7b (Leinonen et al., 1979; Hyva¨rinen, 1981; Dong et al., 1994), and TPOc (Bruce et al., 1981). S2cx, S2 complex (cf. Burton et al., 1995; Krubitzer et al., 1995).

 

 

Human Homologue

 

    There is some evidence ([6]) from human fMRI studies that areas in the depths of the IPS are highly involved in polymodal processing.  Like the monkey area, VIP in humans responds to visual motion towards the face as well as tactile stimulation of the face.

 

 

Glossary

 

    * Architectonic delineation: Delineation of an areas architecture using broad differential patterns like extent and type of myelination, immunohistochemistry, acetylchorlinesterase staining, etc.

    * Cytoarchitectonic delineation: Delineation of an areas architecture according to cell type.

    * Fundus: The trough, or bottom, of a sulcus.

    * Immunohistochemistry: Staining method which stains groups of cells with similar immunoreactivity to various antibodies.

 

 

References

 

[1] J. Lewis and D. Van Essen, Journal of Comparative Neurology, 428, 79 (2000).

[2] J. Lewis and D. Van Essen, Journal of Comparative Neurology, 428, 112 (2000).

[3] C. L. Colby and J-R Duhamel, E. Goldberg, Journal of Neurophysiology, 69, 902 (1993).

[4] C. L. Colby and R. Gattass, C. R. Olson, C. G. Gross, Journal of Computational Neurology, 269, 392 (1988).

[5]  G. J. Blatt and R. A. Andersen, G. R. Stoner,  Journal of Computational Neurology, 269, 392 (1988).

[6] F. Bremmer, A. Schlack, N. J. Shah, O. Zafiris, M. Kubischik, K. Hoffmann, K. Ziles, G. R. Fink, Neuron, Jan. 29, 287 (2001).

 

 

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