On the functions of the cerebrum: the occipital lobes

Front matter

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PRINCETON, N. J. ,

Division lB.FZ\

Contents

Introduction . i

The occipital lobes . 3

The localization of function in the occipital lobe . 9

Introduction

On account of the lack of information in regard to the func¬ tions of the areas (visuo-psychic) believed by histologists to be closely connected with the visual center (calcarine area), it ap¬ peared advisable to attempt to determine the functions of this so-called psychic area, and it was this problem which originated the present work. Subsequent developments directed the inquiry into other channels, and eventually it became imperative to rein¬ vestigate the whole occipital lobe. Only part of the work has been finished but sufficient has been accomplished to indicate that the histological differentiation has not the physiological import which the histologists impute to it. The present work deals main¬ ly with the relations of the lateral aspect of the occipital lobes in the monkey to certain sensory and perceptual states.

In this work eight monkeys were used, each of which was trained in visual discrimination previous to the extirpation or the destruction of parts of the occipital cortex. These animals were purchased from a New York dealer, and, as far as could be ascertained, had not been used for experimental purposes or for pets before the time of purchase. All the animals were reported to be about six to nine months old at the time they were receiv.*i, although in size there was a considerable variation. During the nine months following their purchase they were utilized by Dr. W. T. Shepherd in psychological investigation, and after that period they were entirely in my charge. During the time they were under my observation they were fed mainly by me, but at other times by three other people. The animals were, therefore, well acquainted with the experimenter and they acted in as normal a manner as could be expected from animals kept in captivity. The observations of the animals continued for about fifteen months, at the end of which time all had been operated upon and killed. The animals lived, therefore, approximately two years, during which time they were under almost constant observation,.

MONKEYS although the experiments to be reported in the present paper were not being conducted throughout all this period.

Two of the animals upon which operations were performed were shown at meetings of scientific associations, monkey 7 at the meeting of experimental psychologists in April, 1910, and monkey i at a meeting of the Georgetown University Clinical Society in February, 1910.

During the time the animals were under my observation they were kept in pairs or by threes in cages, 114 cm. high, 90 cm. wide, and 58 cm. deep. The front and right hand ends of the cages were covered with chicken wire, of one and one-half inch mesh. The top, the bottom, the back and the left side were boarded. Within the cage there was a shelf 30 cm. wide jutting from the back of the cage at a height of about 45 cm. This shelf extended the width of the cage. From the front of this shelf to the floor of the cage was a sliding door. When an experiment was to be conducted one of the animals (the one not working) was induced to get below the shelf, the sliding door was closed behind it and the monkey confined beneath, leaving the second animal free so that the experiments might be conducted without interruption and without disturbances.

The sliding door was kept open except at the time of the ex¬ periments, and the animals, which lived in these cages during the progress of the experiments, ran in and out of this space as they wished. There was, therefore, no cause for alarm on the part of the animal which was confined. The animals were not handled and the environment, except for the presence of the experimenter, was kept fairly constant throughout the day. Food and water, other than that used in the experiments, were pushed through or under the wire front of the cage and the animals took as much food as they wished.

Notwithstanding the animals were not handled, all became fair¬ ly tame, they would hang upon the wire netting of the cage and take fruit, nuts, bread, etc., directly into the mouth, and at no time did they appear to be disturbed by the presence of the ex¬ perimenter.

In the accounts of the work which will be found in the section dealing with the observations of the animals before and after the t .

operations, it will be found that there are many expressions simi¬ lar to those used in describing the actions of man. It must not be understood, however, that these expressions are used in the same way they are used for man, but solely for convenience and for brevity. It would, perhaps, have been advisable to describe the actions of the animals, but such descriptions to be intelligible must be accompanied by equally minute descriptions of the situa¬ tions, and from the visual side can best or accurately be shown only by means of motion pictures. It must be understood, how¬ ever, that the anthropomorphic method of describing animal activity is not to be taken as an indication that the animal had the same sort of mental process which a man would have under simi¬ lar circumstances, but even the most careful of the animal psy¬ chologists have found it impossible to dispense with terms des¬ criptive or indicative of mental processes in man. It would, for example, have been better to say “the animal turned its head and its eyes in different directions” rather than “the animal peered around the cage” but, on the other hand, with the warning that has been given, no one should interpret the animal activity in a way other than in terms of movement.

METHODS

Training. To one who is familiar with the studies on the functions of the cerebrum, it is evident that many of the differ¬ ences in opinions and in conclusions have been due to the fact that the tests of animals upon which experiments have been made have been of such a character that they permit of more than one interpretation. It is certain that simple observation of animals following extirpation of parts of the cortex or following the injury to other parts of the nervous system is an inadequate method. For the reason that both the description of results of previous physiological work on the association areas were lacking in exactness and definiteness, about ten years ago, the writer (16-20) devised a method to determine more accurately the sen¬ sory and associative functions of parts of the nervous system, especially of the cerebrum. The first investigation to be per¬ formed by this method was one on the association functions of the frontal lobes (16, 17), but the method has been applied to

TRAINING METHODS sensory functions both in the present work and in work published by others. This method has previously been described in various places and at present it may be said that it depends upon the formation of definite associations in an animal and the determin¬ ation of the presence or absence of the associations after lesions of the nervous system. It will be readily appreciated that by this method there is an approach to the method the clinicians use in the examination of their human cases, and there is afforded the possibility of obtaining very exact information regarding the sensory or associative processes of animals even though in animal experimentation we are hampered, as compared with the investi¬ gations on man, by the lack of the definite means of communica¬ tion by speech.^

Before an animal is operated upon we must become acquainted with its mental character, we must know the animal well before we operate so that we shall be better able to notice deviations from its normal mental character, following, let us say, the loss or the destruction of a certain amount of a certain part of the brain or the spinal cord. Usually it is not possible to keep a laboratory animal for a period of months or years in order to

“ This method was used to a limited extent by a number of investigators before it was applied by me to the investigation of the frontal lobes, but all who had previously used It had employed it in much the same way as they made their regular observations. From the account given by Kalischer (36) of an investigation of the functions of the temporal lobes by this method, It might appear to one unacquainted with the situation that he were the originator of it. He calls it “meine Dressurmethode.” To an impartial observer it appears a mere hair splitting matter to differentiate Kalischer’s method of testing hearing in dogs from that of Thorndike (71), but through¬ out all of Kalischer’s work there is evidence of total ignorance of the work which has been performed in America on animal psychology. It is of interest to note that following a critical note by me (20) Kalischer (37) relinquishes claim to the method as a whole, but makes a claim that he has used the most simple movement as an indication of the presence of sensation in the animal. This claim, in the way it is made, I am sure no comparative psychologist will admit, for the movement of the paw, or the movement of walking, is just as simple physiologically as the movement which Kalischer has used, viz., that of the snapping up of food, which must have associated with it other movements of the head. It is also of interest to note that Kalischer admits in his second article (37) some acquaintance with the training method that had been used by others (e. g., Gaule, 21), although no mention is made of this in his first article.

SHEPHERD IVORY ERANZ get acquainted with its mental make-up, and to facilitate matters we have at our command the training method devised by Lloyd Morgan and so ably followed out by Thorndike (71) and many others. By the use of this method we may have animals, which are to be operated upon, form certain associations, the presence or absence of which can be later determined by the experimenter in a few minutes. The associations always involve two elements, the sensory or afferent, and the motor or efferent. It is believed that in most, if not all, cases a third element is present, viz., the associational. By proper combinations and by the formation of more than one habit at a time it is possible to differentiate these three elements, and to infer without question which of the ele¬ ments is lacking and which has been interfered with.

Comparative psychologists have investigated the visual dis¬ crimination ability of monkeys, but some have not been satisfied from the results and the methods of the experiments that mon¬ keys discriminate colors as such. The methods of other investi¬ gators and the results obtained by them indicate that monkeys have good visual discrimination, although a few are unwilling to admit the conclusiveness of the experiments on color. It seemed advisable to have the animals acquire a habit indicative of color discrimination but none of the methods previously employed ap¬ peared to be sufficiently well accepted and none appeared to place the animal in a position similar to that it might normally be in. In the present work an attempt was made to have the animal test¬ ed in as normal a way as possible, and to form the habit or to produce the discrimination quickly as well as naturally.

In the present work it was necessary to have the animals form habits of a definite visuo-motor character. For this reason the sensory part was made as simple as possible, viz., foods of dif¬ ferent colors, which had to be discriminated. In a series of experiments on the color discrimination of monkeys, conducted by Dr. W. T. Shepherd (68), under my direction it was found that the animal rapidly learned to discriminate colored objects if the stimuli were of a character to attract and to hold the atten¬ tion. In most animal experimentation it has been found difficult to get stimuli which will attract the attention of the animal, stimuli which are appreciated by the animal and which will lead

TRAINING METHODS to definite reactions. In color experiments it has been customary to use the box method of feeding, the box being covered with colored paper or lights being exposed near the box. The employ¬ ment of this method has certain advantages and certain disadvan¬ tages that are apparent to all who have used it. On the one hand the colors may be changed to a considerable degree both in inten¬ sity and in hue, but on the other hand the use of papers, filters, or other similar means of giving stimuli introduces an element foreign to the animal mind and must have less effect than the exhibition of colors in direct connection with the object to be obtained. Moreover, in order to determine discrimination ability many investigators have found it necessary to punish the animal for a wrong selection and to reward it by means of food for a correct selection. In most of the work which has been reported the punishment has also been something foreign to the animal mind, and the use of electric shocks and other similar methods to inhibit the activities of an animal have led at times to disturb¬ ances in activity which are not conducive to proper experimenta¬ tion.

Because of the difficulties and disadvantages of the methods which have been previously employed, colored food was used in the experiments of Dr. Shepherd, and in these experiments it could not be doubted that the attention of the animal was directed toward the stimuli. In the early work bread or rice was mixed with appropriate colors, two or more differently colored pieces of food were simultaneously displayed before the animal and the animal learned to select one or more of the colored pieces. The artificial method of punishment was discarded in these experi¬ ments and a more natural method was employed. In the method the punishment and the cause of the inhibition of the wrong re¬ actions were contained in the stimuli and were not extraneous. Certain of the colored foods were soaked with a solution of qui¬ nine and others had added to them a certain amount of saccharine. On the assumption that the monkey likes sweet and dislikes bitter tasting foods, we should find that the animal would learn to de¬ cline the bitter food and to take only those which were sweet or at least not bitter. As a matter of fact, this assumption was found to hold in almost all the animals tested. With only one monkey was there any difficulty in the establishment of the habit to take the properly colored and sweetened food and to leave the food which had been made bitter. This animal seemed to have little objection to the bitter taste and for a relatively long time ate both the sweet and the bitter foods. This animal died before the effects of the operation were determined and the records are not included in the accounts of the experimental work. Eight other monkeys, however, had a decided dislike for bitter food, or to express this in terms of reaction, these animals soon learned to permit the bitter foods to remain on the plate, and although hun¬ gry, did not touch them. In the formation of the habit and in the subsequent tests following the operation the monkeys were not kept in a state of absolute hunger, for it was found by pre¬ vious work that this factor would interfere with the normal work¬ ing of a monkey.

In performing the experiments to be described here the animal was in its usual cage. The cage has already been described. The animal sat upon the shelf, sometimes near the wire netting on the right hand side and sometimes farthest away from the netting. A glass plate, 12.5 by 18 cm., was arranged on a platform with cup hooks to catch the wire of the cage so that it could be at^

Fig. 9. Glass plate and holder for the presentation of food to the monkeys.. A, glass plate; B-B, cup hooks to catch upon the wire netting of the cage.

TRAINING METHODS tached to any part of the front or side of the cage. The arrange¬ ment was such that the glass plate was kept horizontal. Fig. 9 illustrates the glass plate and the holder. All this part of the apparatus was colored black. The food was placed upon the glass plate, the holder was arranged on the cage and the experi¬ menter moved away from the cage about a meter’s distance. The animal, which usually sat at the farthest end of the platform, moved forwards and took the food which was presented to it on the plate. In performing the experiment in this manner the greatest possible freedom was accorded the animal, and the move¬ ment to be performed was as simple as possible and one which would give the right to conclude that discrimination did or did not take place, i. e., the taking or leaving of the food. The arrange¬ ments at a later date were made more simple, as far as the ad¬ justments are concerned, in that the glass plate holder was at¬ tached to the cage at the beginning of the series of tests and kept there throughout the series on that day. When this was done the food was placed upon the plate in the same manner as has been described. In all the series of tests the arrangements of the breads were constantly changed, the bitter being at times on the right, at times on the left, and if three or four pieces were simultaneously displayed the bitter pieces were between the sweet, or at both ends. In most of the experiments, all of those in which the animal was being trained, the two or more pieces of food were placed upon the plate at approximately the same distance from the cage netting. In later tests at times the foods were arranged indiscriminately on the plate, the sweet being farther from or nearer the cage, etc. Most of the animals were trained on the discrimination of colored foods, and one on the discrimination of foods of different sizes.

The colored food. After a number of tests it was found that white bread was most suitable both for coloring and for food. The bread was usually 24 to 48 hours old at the time it was received. The crust was removed and the bread was cut into thin slices about 5 mm. thick, then into strips of about the same width, and finally into shorter lengths making hexahedrons, approximately cubes, 5 mm. on each edge. A large number of these were cut at one time and from 30 to 100, depending upon the number of animals under the test, were colored; the remain¬ der were used on succeeding days. If kept uncovered the small cubes dried, but it was found that the immersion into the solu¬ tions brought them back to their original size. The cubes were dipped into watery solutions of different colors, and thoroughly saturated. The resultant colors were fairly homonymous, but did not have the smoothness of colored papers or of other similar material on account of the small bubble holes in the bread. The colored moist breads were placed in small crystallizing dishes and covered with watch glasses to prevent the entrance of dust and to limit evaporation. In this way it was found possible to make up fairly large quantities of the different colors and to keep them fresh and moist for several days.

In the general experiments on color four differently colored breads were prepared : red, blue, green, and yellow. The color solutions, formulae for which follow, were made up in large quantities, and to each solution a proportionate quantity of alco¬ holic solution (5%) of thymol was added. The thymol was added for two reasons ; first to prevent the formation of mold in the solution and, secondly, to overcome any special odor of the solution and to substitute for the special odor that of thymol. In this way an attempt was made to equalize the odors of all the stimuli, in order that the discrimination might not take place be¬ cause of the differences in odor. Particular attention is cahed to this factor, for although we have no right to say that by this introduction of a foreign odor (distinctly perceptible to man) the odors of all the pieces of bread were the same, I believe the strength of the solution was sufficient to overcome any odor of the individual solutions. None of the individuals (men) who were tested could detect the least difference in the odors of the solutions, and the tentative conclusion was drawn that the indi¬ vidual odors of the solutions were overcome, and that all the breads smelled alike.

The formulae used in making the solutions were as follows :

Red : Congo red i.o gram.

Water . . .

Saccharine

3.0 grams.

TRAINING METHODS 33

Blue; Toluidin blue . 0.5 gram.

Water . 400.0 cc.

Saccharine . 4.0 grams. ;

Yellow : Methyl orange . 0.5 gram.

Water . 250.0 cc.

Quinine bisulphate (0.5% solution) . 25.0 cc. j

Green : Methyl orange . 0.2 gram.

Smaragd griin . o.i gram.

Water . 250.0 cc.

Quinine bisulphate (0.5% solution) . 25.0 cc.

When they were intended for use, i. e., for the dipping of the bread, the solutions were diluted to one-half strength by the addition of water.

Immediately after dipping the breads the colors of the breads were compared with the colored papers in the Milton-Bradley series. On this comparison it was found that the yellow bread was approximately half-way between the yellow orange and the orange yellow of that scale, but after slightly drying the color was more nearly like the latter. The red bread was approximate¬ ly like the red of the scale, although on account of the chemical properties of the Congo red this color varied to a greater extent than did any of the others. When the bread was dipped into the blue solution it took a color most like that of the Engine colored paper 5b of the scale, being close to the regular blue shades nos.

1 and 2. When the solution was diluted to half strength, as usual, the bread became nearly like Engine colored paper 5, or like the blue of the regular scale, although the latter was a trifle darker. The bread, after having been dipped into the green solu¬ tion almost exactly matched green yellow shade i, but on stand¬ ing this color changed to yellow green shade 2, and eventually became almost like yellow green. The change in this case was probably due to some combination with the air, probably oxida¬ tion.

No special examination of the colored solutions by means of

^"The colors of the breads are given in terms of the nearest color in the Milton-Bradley scale, but the comparison is rough, and in the case of green 2, the color scale showed nothing to correspond closely. The color of green

2 was much darker than the M-B green shade no. 2, but there is nothing irr that scale to give a better idea of the color and shade. The difference in the colors, is, however, the main fact to be remembered.

the spectroscope or by the photometer was made, because all the colors are standard colors, and can readily be made by anyone, and because this examination was not deemed of importance in the present work.

Color Vision of the Monkey. It has been said above that the animals soon learned to discriminate the colored breads, leaving the bitter ones and taking the sweet. At first this may be taken as sufficient evidence that the discrimination was made on the basis of the color quality, but to this conclusion many animal psychologists will take exception. On account of the doubt on this point a supplementary series of tests were made with several monkeys to determine whether the hue or the difference in inten¬ sity (or brightness) was the factor which was discriminated. The tests of one animal will suffice to make this matter clear.

With this animal breads colored red and green were employed. After the animal had learned to discriminate the two kinds of bread, the colors were changed in intensity or in saturation and additional tests were then made. In the original tests (before the changes in the intensity, etc., of the colors) in making up different lots of colored breads the pieces showed slight differ¬ ences in intensity and in saturation, and to a greater extent in moisture. These variations were not of sufficient amount to be particularly noticeable by me or by others, and were determined only when the breads colored at different times were placed side by side and examined in very bright light. There was also a veiy slight difference in the colors of the individual pieces of bread, but under the most favorable conditions these differences could not be detected at a distance of about a meter. In per¬ forming the experiments the colors were placed on the plate sim¬ ultaneously but in an irregular position; half of the time the red was to the right of the animal and half to the left. Sometimes the red and sometimes the green was nearer the animal. In this way no association could be formed between positions and the tastes.

Experiments in color (beyond these performed by Dr. Shep¬ herd, to whose work reference has been made) began with mon¬ key 6 on November 30. On that day in the first test the animal took both pieces of bread, red and green, and immediately placed them in her mouth and ate them. She did not appear to enjoy the

COLOR VISION OF THE MONKEY taste of one of the pieces and became more cautious after two trials, and on the third trial she partly rejected the green (bitter). On seven other trials on this day the animal took only the red bread (sweet). On the following day she took only the red. Three days later she took both the red and the green in the first seven trials, and only the red the other three trials. A rest of two days was given, and, following this, on twelve successive days, ten trials each day, there were only three mistakes. At the end of this time it was concluded the habit was firmly established. The animal would not take the green bread, no matter what posi¬ tion it occupied on the plate. At times the red bread was placed as far away as possible, and at other times to the extreme right or to the extreme left while the green was in the most prominent place, viz., the center of the glass.

On the following day the conditions of the experiment were altered. Instead of presenting to the animal only the definite col¬ ors with which it had become familiar and to which it had learned to react in a definite way, marked variations of these colors were presented. Each of the stock solutions for this experiment was mixed with different quantities of water, and in this way there was obtained solutions giving (to man) four distinct shades of red and four of green. The mixtures which gave the different colors and the color results on the bread (according to the Milton- Bradley scale) of saturating the bread with these mixtures are as follows :

Red I — (red, shade no. 2) 16 cc. standard red solution, 40 cc. water, and a piece of sodium carbonate the size of the head of a pin.”

Red 2 — (red) 16 cc. standard red solution, 40 cc. water, and sodium carbonate until the solution began to clear.

Red 3 — (orange red) 16 cc. standard red solution, 40 cc. water, and sodium carbonate until the solution became clear.

Red 4 — (red, tint no. 2) 10 cc. standard red solution, 50 cc. water, and sodium carbonate until the solution became clear.

Green i — (yellow green, shade no. 2) 20 cc. standard green solution and 50 cc. water.

”The Congo red is an indicator for acids and alkalies, and the color ot the solution depends upon the relative amounts of these opposing conditions. The color of the solution was readily altered by the addition of small quanti¬ ties of sodium carbonate and the greater or less quantity of this alkali gave the various shades and tints of the red.

Green 2 — (green, shade no. 2) 35 cc. standard green solution, and 20 cc. water.

Green 3 — (green, tint no. i) 15 cc. standard green solution, and 25 cc. water.

Green 4 — (yellow green, tint no. i) 10 cc. standard green solution and 50 cc. water.

Two of these colored pieces of bread were presented to the monkey in the same manner as the breads to which it had learned to react. The breads were selected and arranged in an irregular order ; red i and green i ; red i and green 2 ; red 2 and green i ; red 3 and green 3, etc. With these combinations twenty tests were made and in every test the animal took the red bread and disregarded the green. Twenty tests on each of two succeeding days gave the same result; green of any shade or tint was not taken, the red bread of any shade or tint was taken. Three days later twenty-two tests with two of the colors gave almost the same result, and two tests in which two pieces of green and two pieces of red were presented simultaneously showed that the ani¬ mal would take the red and disregard the green even when the conditions of the test were changed in this particular. Follow¬ ing is a record for this day: