The somatosensory system is responsible for sensation such as touch. It is a subset of the sensory nervous system that represents the visual, olfactory, auditory, and gustatory pathways discussed in Chapter 6. There are five types of somatosensory receptors: mechanoreceptors, proprioceptors, pain receptors, thermoreceptors, and chemoreceptors.

Viewing the neuron as an electrical system gives an easy handle into modeling the generation and transmission of action potentials. In the simplest version of this framework, the entire neuron can be viewed as having a single membrane potential. Models built on this assumption are termed “single-compartment” models. A more detailed assessment of the spatial variation in membrane potential gives rise to “multi-compartment” models. We now look at the basic electrical properties of spiking neurons that are essential to most models

Functional neurosurgery is the branch of neurosurgery that seeks to restore or improve neurologic function by manipulation of neural activity. Here we provide a brief review of the pathobiology of the disease processes functional neurosurgery addresses: movement disorders including Parkinson’s disease, essential tremor, and dystonia, epilepsy, chronic pain, and psychiatric diseases including obsessive compulsive disorder, depression, and addiction. We also review emerging applications of neurosurgical techniques including deep brain stimulation not yet prevalent in clinical practice including brain–computer interfaces and disorders of consciousness. Finally, we discuss emerging technology likely to be useful in this rapidly advancing field, including high-density neural recordings, gene therapy, optogenetics, and stem-cell therapy.

As we will learn, cognitive neuroscience had very humble beginnings back in the time of the Romans, and was essentially dormant for close to two millennia thereafter. A surge of interest in anatomy, and the brain in particular, overtook scientists in Europe in the mid-1800s, pushing the field forward. This time period coincided with interest in mapping brain structure to function and description of brain circuits that form the foundations of cognitive neuroscience today. The need to serve the veterans of two World Wars, encompassing regions across the planet, led to a worldwide examination of the behavioral consequences of brain damage. Toward the end of the twentieth century and continuing on until today, an explosion of methods has allowed scientists for the first time to link brain structure and function to mental function in neurologically intact people.

The life story of Muhammad Ali (Figure 4.1), one of the twentieth century’s most famous boxers, interweaves not only boxing and politics, but also the neural basis of motor control. Ali, who was known as Cassius Clay before his conversion to Islam, rose to prominence as an Olympic boxer, eventually turning pro and becoming a world champion. Ali said that his boxing strategy was to “float like a butterfly, sting like a bee,” meaning that his fancy footwork allowed him to flutter around the ring, evading his opponents’ punches until he could move in for a knockout. At the height of his career, Ali was drafted to serve in the US armed forces in Vietnam, but he refused induction because of his religious beliefs. Convicted of draft evasion, he was stripped of his boxing crown and not allowed to box in a sanctioned match for the next three years.

In this chapter, we consider different definitions of bilingualism, underscoring the reality that there are various aspects which should be taken into account when investigating bilingualism, particularly when designing studies and choosing participants. Bilingualism is a complex construct and should be viewed on a continuum. Crucially, many key details about bilinguals’ backgrounds need to be reported in studies to make results comparable and clearly linkable to the specific study sample. Relative proficiency level seems to be the most influential factor, but it is by no means the only factor relevant for studying bilingualism. Rather, individual differences and their variability, dynamically related dimensions and their interaction over time, speech environment and their changes, language use habits, socioeconomic background, and so on have been reported to influence language processing and even brain function to some extent.

The seemingly bizarre behavior displayed by the gentleman in this story can be attributed to a syndrome known as hemineglect or, in its less severe forms, hemi-inattention. Despite having intact sensory and motor functioning, people with hemineglect do not pay attention to one side of space. Hemineglect is considered to be mainly a spatial phenomenon, because the neglect of information occurs with reference to a spatial frame (i.e., information contralateral to the lesion is ignored) and because all types of information, regardless of modality, on the neglected side of space are ignored. Given what you learned in Chapter 7 about the important role that the parietal lobe plays in spatial processes, it should not surprise you that hemineglect often involves damage to the right parietal lobe.

At this point, you are probably wondering what strange disorder this woman has. As you think about this story, a number of possibilities may come to mind. Could she be blind? This seems unlikely. She recognized the pizza (by its distinctive round shape and red color) and incorrectly grabbed an item that looked similar to the apple pie, a package of tortillas, rather than something quite different in shape and size, like a milk carton. Another possibility is that she has a memory problem, such that she can’t remember the features or locations of objects. But this possibility seems unlikely, too. She remembered the locations of the stove and the sink. Furthermore, her memory for objects must be intact because she recognized the apple pie as soon as she smelled it and the kettle as soon as she felt it.

The case history in the opening vignette describes the maternal grandmother of one of the authors (M.T.B.). Although the disease was never formally diagnosed, she surely had Alzheimer’s or some similar dementia. In many ways, her case was typical, characterized by loss of memory, difficulties in spatial processing, disorientation, and changes in personality, especially paranoia. The course was unremittingly downward, although she died from heat stroke before becoming totally bedridden.

In this chapter, we discuss disorders, such as Alzheimer’s disease, that are distinct from the neuropsychological syndromes covered elsewhere in this book. In our discussions so far, we have emphasized the breakdown of specific cognitive functions, such as visual recognition, and precisely described the circumscribed nature of the deficits.

Language is the mental faculty that many people consider most distinctly separates us from other species. Language has also long been studied by scientists. Symptoms like those experienced by Bill Rieger and Jim Hurdle first led Paul Broca in the late 1800s to realize that the hemispheres have different functions, an event that heralded the advent of modern-day neuropsychology and cognitive neuroscience. Broca noticed that a lesion to a specific region of the left hemisphere causes a loss of fluent speech even though the person’s speech comprehension is relatively spared. This syndrome, known as Broca’s aphasia, has provided a window to understanding the neurological organization for language.

Aphasia is the loss of a language processing ability after brain damage. In this chapter, we discuss a variety of aphasias, gleaning lessons about the neurological organization for language.

In this book, we explore how the neurological organization of the brain influences the way people think, feel, and act. Critical to our understanding of the link between brain and mind is cognitive neuroscience, which comprises investigations of mental functions linked to neural processes, ranging from investigations in animals to humans and from experiments performed in the laboratory to computer simulations. Much earlier work in this area comes from human neuropsychology, which examines changes in behavior as a result of brain trauma.