Premotor Dorsal

Nomenclature, Location, Function, Connectivity

Nomenclature:

PMd; areas F2 and F7

Location:

1) F1 -> F2 boundary

a. ~ superior precentral dimple (prcd)

b. drop in numbers of giant layer V "Betz" cells

c. sharp increase in threshold for ICMS

2) F2 ventral -vs- dorsal

a. probably ~~ "arm" -vs- "leg" regions

b. border not visible w/ nissl stain

c. F2v has SMI-32⁺ layer V cells. May correlate w/ fast-conducting projection neurons for "arm" part of F2.

3) F2 -> F7 boundary

a. slightly anterior to genu of arcuate

b. increased lamination in F7

Function:

Hypothesized function: Selection of action based on arbitrary cues

	F2-prcd	F2-vr	F7
Dominant task-related	mvt onset	delay (directional)	instruction (directional)
Sensory responses	proprio. limb	proprio/tactile limb visual (limb conting)	visual (not contingent on limb movement)
Lesions/inactivation	impaired conditional association (arbitrary SR mapping) [Halsband and Passingham '82, Petrides '82, Kurata and Hoffman '94]

1. Proprioceptive signals

Static arm posture influences firing rates (Crammond and Kalaska '96 EBR 108:45)

2. Gaze signal

79% of delay period activity is modulated by position of eye in orbit. Sampled only PMdc. [Boussaoud '95 J Neurophysiol. 73: 886-890]

3. Instruction, delay, and early mvt-related activity correlates w/ target direction (not limb)

Limb direction-related activity is more common in M1. Sampled only PMdc - peri-precentral dimple. [Shen and Alexander '97 J Neurophysiol 77:1195]

4. Even when stimulus location isn't task-relevant, PMd activity is affected

[Boussaoud and Wise '93, di Pelligrino and Wise '93, J Neurosci 13:1231].

5. But, motor significance also affects most PMd activity

Instruction and delay-related activity is influenced by whether movement is required [Kalaska and Crammond '95] and by what movement is required [di Pelligrino and Wise '93, J Neurosci 13:1231]. Reflects "motor significance of nonspatial visual stimuli."

6. PMd activity develops during learning of a new arbitrary SR mapping

Activity differs between early correct responses (chosen by "guess") and late responses (after a new SR rule is learned) [Mitz et al '91, J Neurosci 11:1855]

7. Motor signals (preparatory and command) are task- or context- contingent

PMd movement-related activity preferred visually-guided sequences. When the same sequence is guided from memory (i.e., no visual instruction) few PMd cells show movement-related activity [Mushiake et al '91 J Neurophysiol 66:705].

Connectivity:

1) Inputs (using Pandya and Seltzer '82 as in original anatomy w/ inferred Lewis and Van Essen '00 in parens when different).