"PEa": Older terminology. PE originally encompassed the entirety of the superior parietal lobule (SPL) including the entire medial bank of the intraparietal sulcus (IPS). Pandya and Seltzer (1982) found several architectonically distinct subregions: PEc, at the dorsocaudal pole of the exposed SPL, PEa, covering the medial bank of the IPS, PEci, on the dorsal part of the medial bank, and PGm, ventral to PEci on the medial surface.
"MIP": This is an area that has been carved out of PEa. The name was first assigned by Colby et al. (1988) as a parietal area sending connections to area PO (now V6/V6A, see my other notes). Since that time, physiological and architectonic studies of this part of the brain tend to fall under the rubric MIP, although anatomical studies (eg Lewis et al. 2000) usually place MIP in the posterior half of the medial wall of the IPS and assign the anterior part of the medial bank to area 5v, which is the Brodmann's designation. (Figure this out...)
"PRR": Functional definition used by the Andersen to describe an area with reach related activity. (PRR stands for 'parietal reach region'.) In recent publications, Andersonians have been cautiously estimating that PRR included MIP as well as possibly V6A or MDP (Snyder et al. 2000), although as far as I can tell they have never published a figure of their recording sites.
MIP/PEa is in Brodmann's area 5. If PRR includes V6A as well as MIP, then it extends into Brodmann's area 19. Not sure about the Brodmann assignation of MDP.
Whatever you want to call this part of the brain, it is on the medial bank of the IPS. The wall of the IPS curves into the midline at its posterior extent, this posterior-facing vertical bank of tissue contains V6 and V6A (PO). Its anterior extent may be defined by the end of forward projections from PO.
"MIP": It seems like not much physiology has been done on MIP outside of the Andersen lab. However, recordings by Colby and Duhamel placed an emphasis on anatomical mappings of response properties across the IPS (although they primarily study VIP), and therefore their data serve as a good complement to the Andersen work, which is very detailed physiologically but frustratingly vague with regard to recording sites.
Summary of Colby and colleagues:
Shoulder of the sulcus:
Passive somatosensory fields on contralateral limb.
"Active somatosensory" - reaching in the dark (could be motor).
Bimodal. Most can be independently activated by visual or passive somatosensory stimuli, although some fire only for active reaching and looking.
Deepest posterior MIP:
Purely visual. Peripheral contralateral receptive fields. Some cells prefer stimuli at "reachable" distances. This is the area closest to the V6/V6A complex, which may not have a clearly defined border.
So: there seems to be a shoulder to fundus gradient of somatosensory -> bimodal-> visual response properties. This is summarized in a fascinating but aggravating figure which appears in many different papers. It is best seen as figure 2 of Colby and Goldberg (1999). The aggravating part is figuring out the spatial axes. Hint: shoulder-to-fundus is top-to-bottom, the anterior-posterior is diagonal: top/center-to-bottom/sides:
Holding eye position constant, PRR cells have "reaching fields" which seem to fire for specific targets/endpoints.
In delayed-reaching experiments, PRR cells show delay-period activity tuned for the eventual target of the reach.
If a saccade intervenes between a cue and a reach in a delayed-reaching experiment, the firing of a PRR cell will "update" if the target moves into or out of its reaching field. (Batista and Andersen 2001)
In multi-reach experiments, PRR cells appear to code for the next reach in the sequence. That is, if the plan changes midway through the delay period, the cell will "update" its firing to respond only to the next intended target. (Batista and Andersen 2001, Snyder et al. 1998)
PRR's target selectivity is better described in eye-centered coordinates than in arm-centered coordinates. (Batista et al. 1999)
All of the above properties of PRRs firing with respect to arm reaching are also true in LIP with respect to saccades. The Andersonian interpretation of this is that the posterior parietal cortex (PPC) codes for the "intention" of different movements, and that furthermore all of PPC encodes in eye-centered coordinates, although these are usually gain-field modulated. This is in contrast to the opinion that PPC actually codes spatial attention.
These are from antero- or retrograde tracings to or from other cortical areas; the author has not been able to find any studies that plant tracers directly into MIP.
MIP is connected to many surrounding proprioceptive and visual areas.
Area 5d (PE+PEc) (Pandya and Seltzer 1986)
PGm " " "
V6 (Shipp et al. 1998)
V6A (reciprocal) (Shipp et al. 1998, Caminiti et al. 1999)
VIP (Lewis and Van Essen 2000b)
MIP sends output to:
PMdr (Caminiti et. al. '99)
PMdc " " "
Aaron P. Batista and Richard A. Andersen
The Parietal Reach Region Codes the Next Planned Movement in a sequential Reach Task. J. Neurophysiol 2001 85: 539-544.
Andersen, Batista, Snyder, Buneo, Cohen
Programming to Look and Reach in the Posterior Parietal Cortex
Chapter 36 of ______________________________________
Batista, AP; Buneo, CA; Snyder, LH; Andersen, RA.
Reach plans in eye-centered coordinates. Science, 1999 Jul 9, 285(5425): 257-60.
Bremmer, F; Pouget, A; Hoffmann, KP.
Eye position encoding in the macaque posterior parietal cortex. European Journal of Neuroscience, 1998. Jan, 10(1): 153-60.
Caminiti, R; Genovesio, A; Marconi, B; Mayer, AB; Onorati, P; Ferraina, S; Mitsuda, T; Giannetti, S; Squatrito, S; Maioli, MG; Molinari, M.
Early coding of reaching: frontal and parietal association connections of parieto-occipital cortex. European Journal of Neuroscience, 1999 Sep, 11(9): 3339-45. Retrograde tracer injections into V6A, PMdr, and PMdc.
Action-oriented spatial reference frames in cortex. Neuron, 1998 Jan, 20(1): 15-24.
Colby, CL; Duhamel, JR.
Spatial representations for action in parietal cortex. Cognitive Brain Research, 1996 Dec, 5(1-2):105-15.
Colby, CL; Gattass, R; Olson, CR; Gross, CG.
Topographical organization of cortical afferents to extrastriate visual area PO in the macaque: a dual tracer study. Journal of Comparative Neurology, 1988 Mar 15, 269(3): 392-413. First use of 'MIP' nomenclature.
Colby, CL; Goldberg, ME.
Space and attention in parietal cortex. Annual Review of Neuroscience, 1999, 22:319-49.
Lewis, JW; Van Essen, DC.
Mapping of architectonic subdivisions in the macaque monkey, with emphasis on parieto-occipital cortex. Journal of Comparative Neurology, 2000 Dec 4, 428(1): 79-111. The 500 pound gorilla of parietal architectonics. You heard it here first.
Lewis, JW; Van Essen, DC.
Corticocortical connections of visual, sensorimotor, and multimodal processing areas in the parietal lobe of the macaque monkey. Journal of Comparative Neurology, 2000b Dec 4, 428(1):112-37.
Pandya, DN; Seltzer, B.
Intrinsic connections and architectonics of posterior parietal cortex in the rhesus monkey. Journal of Comparative Neurology, 1982 Jan 10, 204(2):196-210. First division of PE into PEa etc.
Seltzer, B; Pandya, DN.
Posterior parietal projections to the intraparietal sulcus of the rhesus monkey. Experimental Brain Research, 1986, 62(3): 459-69.
Shipp, S; Blanton, M; Zeki, S.
A visuo-somatomotor pathway through superior parietal cortex in the macaque monkey: cortical connections of areas V6 and V6A. European Journal of Neuroscience, 1998 Oct, 10(10): 3171-93.
Snyder, LH; Batista, AP; Andersen, RA.
Change in motor plan, without a change in the spatial locus of attention, modulates activity in posterior parietal cortex. Journal of Neurophysiology, 1998 May, 79(5): 2814-9. Reach/ saccade trials in PRR and LIP, where on some trials a second command either confirms the saccade/flash or instructs the animal to replace it with the other type of movement. Saw a larger response to the second cue if it countermanded rather than confirmed the first instruction, which supports the argument that PRR and LIP code the next intended movement in a sequence.
Snyder, LH; Batista, AP; Andersen, RA.
Intention-related activity in the posterior parietal cortex: a review. Vision Research, 2000, 40(10-12): 1433-41.