EXPERIMENTAL RESEARCHES ON SENSORY LOCALISATIONS IN THE CEREBRAL CORTEX
Authors: de Barenne J. G. Dusser 
Published: December 2014

1. It is possible to investigate the sensory functions of the cerebral cortex by local application of strychnine.

2. Consequent upon such local application to a certain area, which forms what may be termed the “active zone”of the cortex, constant and typical symptoms of excitation occur.

3. The application of strychnine to parts of the convexity of the cortex outside this zone is not followed by like disturbances.

4. The sensory disturbances produced affect both cutaneous and deep sensitivity.

5. The disturbances in cutaneous sensitivity manifest themselves by (a) Symptoms of spontaneous excitation, paræsthesiæ. (b) Hyperæsthesia and hyperalgesia. (c) Exaggeration of Munk's “Berührungsreflexe.”

6. The disturbances in deep sensitivity manifest themselves in an abnormal hypersensitivity to pinching and pressure of the bones, tendons, and muscles.

7. So far as the sensory functions of the skin of the cat are concerned, both sides of the body are represented in the cortex of one hemisphere, but the opposite side most.

8. The disturbances of deep sensitivity consequent on the application of the poison to the active zone of one hemisphere alone are always unilateral and on the contralateral side of the body.

9. The so‐called “active” zone may be subdivided, according to the parts of the body where sensory disturbances show themselves, as follows:— (a) Head zone: this includes the sensory representation of the neck as well as of the head. (b) Fore‐limb zone: this includes the sensory representation of the trunk as well as of the fore‐limb. (c) Hind‐limb zone. (d) Zone of “crossed symptomatology.” On applying strychnine anywhere in this zone we find disturbances of cutaneous sensitivity provoked in the ipsilateral fore‐limb and in the contralateral hind‐limb.

10. The following parts of the cortex are included in the head zone:— (a) The gyrus sigmoideus anterior. (b) The part of the gyrus sigmoideus posterior in front of the small fissure termed by Campbell “the compensatory ansate fissure.” (c) The frontal half of the gyrus suprasylvius anterior. The gyrus sigmoideus anterior forms the focal area of this zone.

11. Included in the fore‐limb zone are the following parts:— (a) The gyrus sigmoideus anterior. (b) The part of the gyrus sigmoideus posterior in front of Campbell's “compensatory ansate fissure.” (c) The frontal half of the gyrus suprasylvius anterior. (d) The middle third of the gyrus ectosylvius anterior. The focal area of this fore‐limb zone is represented in the parts mentioned under (a) and (b).

12. The hind‐limb zone occupies the frontal half of the gyrus inarginalis. The focal area of this zone lies in its anterior part.

13. The following parts form the zone of “crossed symptomatology.” (a) The part of the gyrus sigmoideus posterior behind Campbell's “compensatory ansate fissure.”(b) A small part of the gyrus marginalis immediately behind the sulcus ansatus.(c) The frontal third of the gyrus suprasylvius medius and a sinall portion of the hinder part of the gyrus suprasylvius anterior.(d) The part of the cortex situated on the transition from the gyrus ectosylvius medius to the gyrus ectosylvius anterior. The more frontally in this zone the application of strychnine is made, the more marked are the resulting symptoms.

14. The fore‐limb and head zones almost entirely overlap one another (contrary to the view taken by Munk and Rothmann).

15. In so far as any sensory zone overlaps the motor area (the position of the latter being decided by methods different from those herein dealt with), there may be said to exist in the cat, and probably also in the dog, a common sensori‐motor cortical zone, as Munk and others have held.

16. The sensory disturbances produced are, in almost all the experiments, most marked towards the distal parts of the extremities.

17. Except in one instance, none of my thirty‐four experiments have furnished any proof of a segmental distribution of the sensory disturbances caused by strychnine application to the cortex.

18. Except in one experiment, no genuine symptoms of motor excitation —such as muscle twitchings, hyper‐reflexia, and exaggeration of tendon and periosteum reflexes—have been observed. This absence of motor symptoms in my experiments, as compared with those of some other observers, may have been due to the fact that in mine the application of strychnine was always slight and the poison was probably confined to the more superficial layers of the cortex.

19. The lobus frontalis has no sensory functions in the cat.