title: Parallel thalamic activation of the first and second somatosensory areas in prosimian primates and tree shrews.
abstract: In Tupaia belangeri and Galago senegalensis, microelectrode recordings immediately after ablation of the representation of the forelimb in the midportion of the first somatosensory area, S-I, revealed that all parts of the second somatosensory area, S-II, remained highly responsive to cutaneous stimuli. In this way, prosimian primates, close relatives of simian primates, and tree shrews differ markedly from monkeys in which S-II is deactivated by comparable ablations, and resemble such mammals as cats and rabbits in which S-II also remains highly responsive following ablations in S-I. Thus, it appears that the generalized mammalian condition is that S-I and S-II are independently activated via parallel thalamocortical pathways. A dependence of S-II on serial connections from the thalamus to the S-I region and then to S-II apparently evolved with the advent of anthropoid primates, and may be present only in monkeys and perhaps other higher primates.
authors.affiliation: Department of Psychology, Vanderbilt University, Nashville, Tennessee 37240.
authors.forename: P E
authors.initials: PE
authors.lastname: Garraghty
authors.forename: S L
authors.initials: SL
authors.lastname: Florence
authors.forename: W N
authors.initials: WN
authors.lastname: Tenhula
authors.forename: J H
authors.initials: JH
authors.lastname: Kaas
mesh_terms: D000818:Animals; D001132:Arm / Q000502:physiology; D001931:Brain Mapping; D004558:Electric Stimulation; D004594:Electrophysiology; D005701:Galago / Q000502:physiology*; D006225:Hand / Q000502:physiology; D008839:Microelectrodes; D009434:Neural Pathways / Q000502:physiology; D012879:Skin Physiological Phenomena; D013003:Somatosensory Cortex / Q000033:anatomy & histology / Q000502:physiology*; D013045:Species Specificity; D013788:Thalamus / Q000033:anatomy & histology / Q000502:physiology*; D014417:Tupaia / Q000502:physiology*