What about the Jennifer Aniston brain cell?
Ever since David Hubel and Torsten Wiesel (Nobel Laureates in Physiology or Medicine for 1981) began their pioneering work on the function of the visual cortex, beginning in the 1960s, we have been confronted with trying to understand where it will all end–how sophisticated will our visual cells or any other cell type become and will we eventually build a single cell so sophisticated that it will be responsible for the identity of our grandmother? If so, should we lose our grandmother cell, will we also lose the capacity to recognize her? Individual neurons in the visual cortex show an increasing degree of sophistication and stimulus generalization as one goes upstream from the inputs that come from our retina. From circular, center-surround cells of retinal origin, the brain begins, not to extract a visual code from the retinal signal, like a morris code interpreter, but rather to use the building blocks of retinal origin and combine them in new ways, as if the visual cortex had access to a massive Lego set with which to construct a lot of different buildings of different architectures, vintages and colors with an increasing degree of sophistication and abstract representation of the visible world. Each building block as an input from the retina. One must keep in mind that the high speed movie we see in front of our eyes everyday, advancing at non-flickering frame rates (at least 30 frames/sec), in vivid color, with textures and contours that are often invented or exaggerated–that amazing scene in front of us is achieved because the brain is a massively parallel processing machine, which uses the continuous information provided by 1.2 million ganglion cell axons emanating from each eye, to achieve an unparalleled performance in visual display and art recognition. Not only are we continuously aware of the detailed visual information in front of our eyes, but we become instantly informed about the emotional content of our brain imagery: images can instantly evoke laughter or tears depending on their content, our visual memories and our emotional capacities. Each year, the Academy Awards fails all of us as humans for not recognizing the features of our visual system that make movie appreciation even remotely possible. Where’s the Oscar? What’s the category?
Vision rules! We are overwhelmingly visual animals, with a visual brain that developed so much power, we eventually learned how to read and through that medium, we began to change the world we live in. Except for hurricanes, volcanoes, tornadoes and the coming global climate change and mass species extinction, we learned to rule the world and turn the tables on the remaining species that had previously hoped to dine on us. Vision controls our brain, even though it tells lies about the visible world around us, through mechanisms such color-constancy, Mach Bands for enhancing edges, contrast gain, chromatic adaption and movement distortion to name just a few deceptive tactics of our visual apparatus. The brain is a plastic organ, waiting to change and develop according to the experiences we present to it. The “lies” are actually generated by the retina’s commitment to improve our edge detection, recognizes boundaries and colors and detect the movement and project the estimated arrival times of moving objects. From stationary retinal inputs, the cortex begins to build larger regions of visual field receptivity. From small circular receptive fields, larger regions of light sensitivity are constructed that are made of lines of different orientation covering a larger retinal region and these respond preferentially to movement in one direction, as well as prefer information from one eye over the other in an organized set of repeated columns. All of the processing that takes place within the visual cortex, with multiple parallel streams of Lego block construction, still represents early coding for some of our most important visually related events.
Brain imaging studies have revealed that a “letterbox” region lies, on the left side of the brain, near the occipito-temporal border that is associated with the identification of letters of the alphabet and words we have learned. It’s estimated that the human word capacity is somewhere between 50,000 and 100,000 words accomplished when we are adults, through the repetitive, daily act of reading and challenging our brain with new words and their meaning. Written language has fundamentally changed the world and contributed substantially to the growth in intellect and the recognition that reading and writing are fundamental to progress. In the hundred years between the 20th and the 21st century, the percentage of people who are literate has increased dramatically and will continue to grow, given the essential entree it provides into advanced cultures.
Outside of the visual cortex per se, in the medial temporal inferior lobes, close to the hippocampus that plays a big role in laying down memories that are eventually stored in the cerebral cortex, memories of the declarative type, available to our verbal recall, researchers have determined the encoding properties of single brain cells which turn out to display surprisingly specialized and unique properties. In the less than 1% of epileptics that do not respond to the litany of antileptic medications, removing the localized offending tissue is the only way to reduce or eliminate seizure activity. But since the legendary patient H.M., neurosurgeons carefully explore an epileptic focus with recording electrodes to make sure they don’t remove essential structures committed to the patient’s memory. At the cellular level, no two brains are wired alike, so one has to be careful and record from the cells near the lesion and avoid removing brain tissue that has stored or can store part of the human engram. These studies, which often require hours with a patient’s brain exposed and recording electrodes inserted into brain structures to explore single cell properties near the epileptogenic site, have revealed surprising properties of human neurons that contain memory information about people. One such cell recently described (Quiroga et al., Invariant visual representation by single neurons in the human brain, Nature, 435,1102-1107,2005) in a patient was the “Jennifer Aniston Cell.” This cell responded to images of Jennifer Aniston very distinctly; it did not require her face in any particular position or special clothing. An image of Jennifer Aniston in any position or posture fired the cell vigorously, whereas other similar images of famous people did not. Interestingly, when the image of Jennifer Aniston was coupled with Brad Pitt, the cell was silent. Not only did the cell respond to an image of Jennifer Aniston, but it responded as well to the auditory or written form of her name. Was this then the long lost grandmother cell we had been searching for during the last 50 years? If you destroyed that single cell, would the patient lose all memory of Jennifer Aniston? Naturally, it was unethical to do something like that, but the authors did feel that their results, with included 993 units, with about 14% of cells committed to human identities (Halle Berry was also popular, as was Bill Clinton, the Beatles and cartoons from The Simpsons and Michael Jordan); to qualify as a human identity cell the cellular response to the picture had to equal to the mean plus five standard deviations of the baseline, with a least two spikes in the post-stimulus time interval. Repetition is the means we have for forming strong, long-term memories. So perhaps all of us have Jennifer Aniston, Halle Berry and Bill Clinton cells. Since the study was done in 2005, the experimenters did not have a chance to look for Obama cells, but by now they are probably there, perhaps in all of us, maybe even more strongly integrated into the brains of tea baggers. The authors argue that their findings favor the interpretation that the cells from which they recorded are in fact, the missing grandmother cells that were postulated to exist, but have never really been found until now. The obvious question that comes up is whether there is more than one representation of Jennifer Aniston? And if one Jennifer Aniston cell is knocked out, will another one quickly takes its place through the methods of laying down a new long-term memory from the background neural engram already active in the brain? One of the most riveting of all issues related to brain function involves the question about the grandmother cell, or in this case the Jennifer Aniston cell. The fact that such a cell exists, when the theory to which I ascribed for many years held that Jennifer Aniston was represented by an overlapping population of cells, so that her identity was determined by a network, not a single, cell has been seemingly shattered by this report. Thus we must now acknowledge the likely fact that we store images of people we know or have seen enough times and encode the representation of these individuals into the discharge properties of a single cell. That cell is so sophisticated that it responds to Jennifer Aniston independent of position, expression, hair style, clothing or facial expression. But, do we have one or many Jennifer Aniston cells in our brain and can those cells be recalled for updating to new folks, once we lose interest in Jennifer Aniston? Of greater relevance is the question about who or what is it that reads the Jennifer Aniston cell to report it to our consciousness? Is the Jennifer Aniston cell one cell removed from our conscious identity? Is consciousness the readout of our cortex, with specialized Jennifer Aniston cells making the task more simplified? Stay tuned! There’s a notable human issue residing in these discoveries. Recordings from awake humans during surgical exploration for epilepsy-related surgery is about the only way we can get at this question and the results of Quiroga et al., have come down pretty hard in favor of us having brains with grandmother cells! But what if we find the same cells in the Chimpanzee? Will that give us pause? Do Chimps care about Jennifer Aniston if they see her on TV enough times? Do we also need language, both written and verbal to even form a Jennifer Aniston cell? All these questions remain in the future, but we can no longer deny the grandmother cells of our present and future brain.
RFM
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