This book is not a general introduction into neuroscience, instead it is an introduction into neurophysiology. The editor, Gordon Shepherd, was the maThis book is not a general introduction into neuroscience, instead it is an introduction into neurophysiology. The editor, Gordon Shepherd, was the main discoverer of neural microcircuits (covered at the beginning of the book) which is just another clue showing that the standard model of the neuron as a summation node with a threshold is way too simplistic....more
Because this book brings in real neuroscience data it is the best book on consciousness yet published. Consciousness is a combination of perception anBecause this book brings in real neuroscience data it is the best book on consciousness yet published. Consciousness is a combination of perception and conscious sensations called qualia, two different phenomena. Qualia is why we see the color blue instead of just blindly react to some neural signals as would zombies (we can do this up to a point in a phenomena called blind-sight which involves a primitive non-cortical neural pathway). One can have qualia without perception but not vice-versa as exemplified when some object pattern suddenly jumps out at you from a picture you have been viewing.
The foundational Qualia (feelings and primary sensations) are not generated in the brain regions that make us intelligent (although our pre-frontal "planning" cortex seems to add a valuation component). Because this book deals with consciousness it mainly deals with the qualia from the primary sensory cortical centers and not the deeper non-cortical feeling centers. "Split brain" patients have separated cortices but unified feeling centers. In a rare case in which both left and right cortices can talk the book reports this:
"this led to frequent back-and-forth between them, as when Mark (the researcher) echoed one of her statements that she did not have feelings in her left hand. She then insisted that her hand was not numb, followed by a torrent of alternating Yes's and No's, ending with a despairing "I don't know". (page 291)
So what is the evolutionary purpose of qualia? Does it use energy even though it is not affected directly by any known energy source (the frontiers of physics are at high energies, not the low energies of the brain)? While this book cannot provide definite answers it does make suggestions....more
The great value of this book is that it is a first hand account of a stroke occurring on one side of the brain in one who has the knowledge to interprThe great value of this book is that it is a first hand account of a stroke occurring on one side of the brain in one who has the knowledge to interpret what happened. The damaged stroke side of the brain is responsible for language and thus most reasoning. This left her non-verbal, intuitive, spiritual side of her brain intact and able to come to the forefront of her personality as she slowly recovered the functioning of her language side. This dichotomy makes for a fascinating read....more
This is a book mostly about the human prefrontal cortex by a leading psychological neurologist who escaped from the Soviet Union. So not only will youThis is a book mostly about the human prefrontal cortex by a leading psychological neurologist who escaped from the Soviet Union. So not only will you get some brain information but also the story of the author's professional life. The prefrontal cortex is responsible for setting and maintaining of goal behaviors. Consequently, it attempts to over-ride immediate emotional response behaviors. It accounts for 29% of the total cortex in humans, 17% in the chimpanzee, 11.5% in the gibbon, 8.5% in the lemur, 7% in the dog, and 3.5% in the cat. (page 33). Since it is the most recently evolved part of the brain its functions like episodic memory is the first to fail with age. It is also the last brain region to mature and it does not become mature until around age 18 (page 144).
The two major syndromes (or end points in a damage continuum) that arise from its damage are the dorsolateral syndrome and the orbitofrontal syndrome. The dorsolateral syndrome (chapter 8)produces pseudo-depression. Like depression this patient has an inability to initiate behaviors. Yet when behaviors can be induced after much effort they tend to persist without stopping. In severe cases the patient will lie passively in bed, neither eating nor drinking. Patients with this syndrome are no longer bothered by pain even though they can describe the pain they feel just like normal people. Most of these patients will also have Anosognosia in which they are unable to recognize their limitations with the result that they have no motivation to undergo rehabilitation exercises. Minor or slowly developing dorsolateral syndromes can be very hard to recognize since people assume that the person is becoming lazy or simply disinterested in things due to age. The orbitofrontal syndrome (chapter 9) is a condition in which the patient is emotionally dis-inhibited and impulsive. They are not able to defer immediate gratification and cannot see the consequences of their actions. They will say what is on their minds without regard to the social consequences as well.
For me the most significant new idea was Goldberg's suggestion that the underlying difference between the two brain hemispheres is based upon their learning rate in response to novelty (page 40). In all learning, a system has to make a trade-off between the speed of learning and the accuracy of learning. Those associations, as formed by conditioned learning, formed after only one or a few observed event correlations have a high probability of being wrong (the correlation could just be a coincidence) compared to associations formed after a longer observation time. It would be advantageous for any animal to be able to work with either the uncertain or certain associations depending on the task at hand. This pre-adaptation of the hemispheres is why language is most often found on the left side because of the tight context rules for grammar. Setting up a context involves making many more associations that cannot be contradictory if context control is to work. In contrast the right side of the brain would tend to be the more intuitive since it works with uncertain associations but these are associations that would not yet exist on the left side. Brain scan observations show that the right hemisphere is more active when a task is novel while the left hemisphere is more active when the task is practiced (page 49).
Overall, a great addition to anyone's neuroscience shelf....more
Despite being over 10 years old now this book by a leading researcher in the field gives some good information on the fear generating system of the brDespite being over 10 years old now this book by a leading researcher in the field gives some good information on the fear generating system of the brain.
The first two chapters review the various psychological movements of the 20th century with the third chapter narrowing that down to how they dealt with emotion. By the mid 1980's (page 53) the experimental evidence was in showing that affective (emotional) reactions could take place in the absence of conscious awareness. The key figure was Robert Zajonc who first demonstrated the phenomena known as the exposure effect in which emotionally neutral things one has previously seen are preferred over novel objects. After this discovery, in another experiment, he presented pictures to people so fast that they had no conscious recollection of what they saw yet they still exhibited this exposure effect. Today we call this subliminal suggestion. Zajonc took this further. By subliminally presenting an emotionally charged picture (a smiling or frowning face) just before a normally presented emotionally neutral picture and doing this for a whole set of pictures the test subjects had a tendency to later either like or dislike the neutral images according to what emotionally charged images was associated with them (page 59). The main point here is that some unconscious brain mechanism is a work and this is what the author, Joseph LeDoux investigated from a neuroscience perspective (this exposure effect is also the main reason why we must endure advertising).
Chapter 6 gets into learning phenomena of conditioning (Pavlov's dog), especially fear conditioning in which a tone is paired with an electrical shock. This chapter finally gets into some neuroscience by describing the pathway of an auditory triggered fear conditioning. The key brain center involved in producing fear responses in all vertebrate animals turned out to be the central nucleus of the amygdala. It receives neuronal inputs direct from the auditory thalamus thus its inputs do not depend on the cerebral cortex. Electrical stimulation increases the heart rate (blood pressure increase), induced animal freezing responses, stress hormone release, and reflex potentiation (they get faster and stronger). Lesions eliminate these responses in fear conditioning experiments. Joseph LeDoux himself further refined these results by showing that the central amygdala's projection to the periaqueductal grey of the brain stem was responsible for the freezing reflex, that its projection to the lateral hypothalamus was responsible for the blood pressure rise. Others showed that its projection to the bed nucleus of the stria terminalis (in the hypothalamic region) was responsible for the stress hormone release. Electrical stimulation of the amygdala in humans most often produces the conscious sensation of fear (page 172). Damage localized to the amygdala in humans is very rare but one such patient was studied by Antonio Damasio. This patient was unable to recognize a fear facial expression even though she could identify all the other major classes of facial expression (page 173).
Chapter 8 is a very good discussion mental illness emphasizing the role that unconscious fear conditioning might play. This is rather obvious for various phobias and stress disorders but this also has a role in producing anxiety and thus depression. The author suggests that panic attacks could be a fear conditioning that improperly treats the body's own autonomic fear responses as a fear producing stimulus (page 258). In learning theory this is known as the "assignment of credit" problem. This is the problem of determining which prior event should be associated with a fear event.
Chapter 9 is a discussion of consciousness that includes the concept of “Working Memory”. Working memory is a more comprehensive idea about short term memory which allows one to remember temporarily up to 7 things at a time for up to a few minutes. In the amygdala it indicates that either more neurons are recruited into the event or the neural activation in the amygdala lasts longer than would be normal. Working memory seems to be controlled by the lateral prefrontal cortex at the very front of the brain which exists only in primates (page 274) so presumably it is able to keep amygdala neurons active longer. Below the prefrontal region is the orbital cortex which seems to be responsible for evaluating an emotional stimulus in terms of longer term goals.
This book first published in French in 1894 is the beginning of the neuron theory of the brain. Prior to this the dominant thought was that the brainThis book first published in French in 1894 is the beginning of the neuron theory of the brain. Prior to this the dominant thought was that the brain was composed of one big interconnected fiber network (a reticulum). This book includes descriptions and illustrations from a wide variety of animal brain locations. The revolutionary technique Cajal employed was the Golgi stain which blackened a small proportion of neurons in a slide section....more