amygdala A collection of bundles of neurons (nuclei) buried deep in the medial temporal lobes of the cerebral cortex, about the size and shape of a walnut. The amygdala are part of the limbic system and are involved in emotional processing and especially in the learning of emotionally salient associations. Aversive emotions, such as fear, are particularly dependent on the amygdala.
Broca’s aphasia (and Wernicke’s aphasia) Aphasias are disorders in the generation (Broca) or comprehension (Wernicke) of language and are associated with damage to different regions of the linguistic brain.
cerebral cortex The deeply folded outer layers of the brain, which take up about two-thirds of its entire volume and are divided into left and right hemispheres that house the majority of the ‘grey matter’ (so called because of the lack of myelination that makes other parts of the brain seem white). The cerebral cortex is separated into lobes, each having different functions, including perception, thought, language, action and other ‘higher’ cognitive processes, such as decision making.
frontal lobes One of the four main divisions of the cerebral cortex and the most highly developed in humans compared to other animals. The frontal lobes (one for each hemisphere) house areas associated with decision making, planning, memory, voluntary action and personality.
hippocampus A sea horse-shaped area found deep within the temporal lobes. The hippocampus is associated with the formation and consolidation of memories and also supports spatial navigation. Damage to this area can lead to severe amnesia, especially for episodic (autobiographical) memories.
insular cortex Meaning ‘island’, the insular cortex is found at the bottom of a deep fold at the junction of the temporal, parietal and frontal lobes. It is involved in detecting and representing the internal state of the body (so-called ‘interoception’) and is increasingly associated with conscious emotional experiences and the sense of self.
introspection The act of observing or examining one’s own mental states. Introspection is a key instance of metacognition.
limbic system An old-fashioned term relating to a collection of brain structures involved in emotion, motivation and memory. These include the amygdala, hippocampus, certain thalamic nuclei and specific regions of cortex.
neurons The cellular building blocks of the brain. Neurons carry out the brain’s basic operations, taking inputs from other neurons via dendrites, and – depending on the pattern or strength of these inputs – either releasing or not releasing a nerve impulse as an output. Neurons come in different varieties but (almost) all have dendrites, a cell body (soma) and a single axon.
orbitofrontal cortex The part of the frontal lobes lying directly above and behind the eyes. The orbitofrontal cortex is involved in the processing of emotional and motivational information, particularly in relation to decision making.
prefrontal cortex The most frontal part of the frontal lobes, the prefrontal cortex is associated with high-level cognitive functions, such as metacognition, complex planning and decision making, memory and social interactions. Collectively, these operations are sometimes known as ‘executive functions’.
somatic marker hypothesis The brainchild of Antonio Damasio, this theory emphasizes the role of emotions in decision making. It proposes that complex decisions rely on the perception of bodily states (somatic markers), which represent the emotional value of different options.
temporal lobes One of the four main divisions of the cerebral cortex. These lobes are found low to the side of each hemisphere and are heavily involved in object recognition, memory formation and storage, and language. The hippocampus is in the medial part of these lobes (the medial temporal lobe).
In the 1950s, a young man, Henry Molaison, was experiencing severe epilepsy. The doctors decided to remove his medial temporal lobes, which were thought to be the source of his symptoms. This successfully treated his seizures, but there was an enormous price to pay. Although his short-term memory (his ability to retain information for a few seconds or minutes) was largely intact, he was unable to form new long-term memories. Consequently, his mind never moved beyond the 1950s and however frequently he visited a new person or place, they would always be unfamiliar. Studies of such patients established the way in which the medial temporal lobes (especially the hippocampus) turn short-term memories into permanent ones, with much of the rest of the temporal lobes acting as a long-term store. Even within these storage areas, there is further fragmentation, with semantic memories (such as what the capital of France is) located in a separate region (the temporal pole) from memories of past events (which are more widely distributed across the temporal cortex). Evidence also shows that different processes occur when we have a sense of vague familiarity about a past event, compared with when we can confidently recall it, and these are carried out by different parts of the medial temporal lobes.
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Many different parts of the brain take on specialist memory functions, according to content (such as knowledge versus past events) or process (such as recollection versus familiarity).
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The prefrontal cortex, regularly associated with complex thought, is also involved in all memory processes. This broad role probably reflects a need for humans to perform various sophisticated memory-based operations, such as generating and using strategies to retrieve faint memories and making assessments about what information is truly important to retain. Consequently, when we obey instructions to forget something, our prefrontal activity increases as our medial temporal lobe activity decreases.
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3-SECOND BIOGRAPHIES
BRENDA MILNER
1918–
The first scientist to study Henry Molaison
ENDEL TULVING
1927–
Pioneering researcher into long-term memory
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Daniel Bor
What is the capital of France? How do I make that chess piece move? Your brain has a specific place for each memory function.
Walking in the woods, you spy a grizzly bear. Fear courses through your body and in an instant you are poised to flee. We might think that seeing the bear causes the feeling of fear, which leads to the charge of adrenaline that prepares us for flight (or fight, if you are brave). Things, however, are not so simple, as William James (and independently Carl Lange) surmised more than a century ago. They argued that an emotion (such as fear) is the result of perceiving changes in bodily state, not the cause of these changes. We feel afraid because our body is preparing to act in a particular way, not vice versa. Although controversial, this idea has stood the test of time; it is now widely accepted that emotions are deeply dependent on how the brain and body respond to each other, and the search is now on for the brain mechanisms involved. One key region is the amygdala, a collection of almond-shape structures buried deep inside the medial temporal lobes, which plays a key role in consolidating memories of emotional experiences. Damage to the amygdala can lead to dampening of emotional responses and especially the loss of fear. Many other neural areas are also involved, including the orbitofrontal cortex, which links emotion and decision making, and the insular cortex, which monitors the body’s physiological condition.
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‘I tremble, therefore I am afraid.’ Emotion is the context-dependent perception of changes in the physiological condition of the body.
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Emotion depends not just on bodily changes, but on the context of such changes. Stanley Schachter and Jerome Singer injected volunteers with adrenaline while an actor in the same room behaved either angrily or euphorically. The lucky ones experienced euphoria; the others, anger. Crucially, those who were informed about the physiologically arousing effects of adrenaline did not experience these emotions. The findings supported a ‘two factor’ theory, that a felt emotion depends on how the brain interprets changes happening in the body.
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3-SECOND BIOGRAPHIES
WILLIAM JAMES
1842–1910
With Carl Lange came up with the idea that emotions are perceptions of changes in bodily state
STANLEY SCHACHTER
1922–97
With Jerome Singer, conducted seminal experiments showing context dependency of emotional experience
ANTONIO DAMASIO
1944–
Reinvigorated the study of emotion with his ‘somatic marker hypothesis’
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Anil Seth
You’re not afraid of the bear. Your heart races and you are in a cold sweat because your body is setting up your fight/flight options.
Einstein claimed that imagination is more important than knowledge. It is a strange mental skill that humans appear particularly adept at. For instance, if you close your eyes and imagine a black cat jumping up a green wooden fence, you will probably generate a surprising degree of detail. But is imagination a special process, distinct from perception, or is it intimately entwined with our senses? The evidence largely points to the latter. For instance, one patient, RV, had damage to the visual colour centres of his brain, causing a brain equivalent of colour blindness. RV was unable to work out what colour snow was when asked to imagine it. Another brain-damaged patient was unable to either perceive or imagine famous faces. Brain-scanning studies have dramatically extended this view, for example, by showing that auditory imagery activates the auditory cortex, similar to if the same sounds were actually heard. And bringing to mind fearful imagery is sufficient to activate the fear centre of the brain, the amygdala. The clear, and evolutionarily efficient, picture is that any part of our brains responsible for direct experience can also be co-opted to aid our imagination.
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Imagination is a powerful, particularly human, skill. But instead of having specialized neural hardware, it is entirely reliant on our existing sensory regions.
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Adrian Owen has revolutionized the study of vegetative state patients. He showed that some of these patients are wrongly diagnosed – they are completely paralyzed but still have an active inner consciousness. Owen tests this by asking questions in the fMRI scanner and the patient answers ‘yes’ by motor imagery (which activates the motor cortex) and ‘no’ by spatial imagery (activating the parahippocampus). Therefore, imagination gives these patients their only chance of a voice.
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3-SECOND BIOGRAPHIES
STEPHEN KOSSLYN
1948–
Cognitive neuroscientist known for his work on mental imagery. He argues that imagination is composed of several different sub-processes
MARTHA FARAH
1955–
Neuropsychologist, who was one of the first to document patients lacking both perception and imagination in specific domains
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Daniel Bor
Just imagine what I could imagine if I had lived a fuller life and gained some more exciting data to play with.
A child prodigy (he graduated when he was 16 and gained his medical degree at 20), Paul Broca was a physician, surgeon and anatomist who spent all of his student years and working life in Paris. His free-thinking, pro-Darwin stance and his interest in anthropology (he founded The Anthropological Society of Paris in 1859) got him in trouble with the Church and state authorities, yet they did not prevent him from leading a successful public life; he was elected to the French Senate and became a member of the Académie de Médecine and received the Légion d’Honneur.
Although he made many important contributions to other fields of medicine (including cancer, infant mortality and public health) it is as a neuroanatomist that he is best remembered. Broca was the first to describe the evidence of trepanning found in Neolithic skulls and made great advances in cranial anthropometry and comparative anatomy of the brain, providing invaluable data on its weight and size.
Broca is best known today as the first to produce reliable, replicable physical evidence of the localization of function in the brain, laying the ground for future research into brain lateralization. Franz-Joseph Gall (who died when Broca was four) had championed the idea of phrenology, the theory that different parts of the brain give rise to different actions emotions and moods. He was a theorist, making inferences from the cranium instead of the brain within. In 1861, after attending a lecture by Ernest Aubertin, a supporter of the idea of localized function, especially of speech, Broca was inspired to look for evidence within. As Professor of Clinical Surgery at the University of Paris, he had access to several hospitals, and in one of them he found M. Leborgne, an aphasic patient who could not articulate speech (although his comprehension was unimpaired). When Leborgne died, Broca performed an autopsy and discovered lesions on the frontal lobe of his brain’s left hemisphere. Further autopsies on a statistically significant number of similar patients replicated the result. This was the first documented evidence that brain functions were localized and that the two hemispheres operated differently to each other (the right hemispheres on the autopsied bodies were all unblemished). The area was named after Broca by the Scottish neurologist David Ferrier.
Subsequent MRI scans that have been carried out on Leborgne’s brain (preserved in the Museum of Mankind in Paris) indicate that there may be more to it than lesions, but they do not diminish Broca’s contribution to neuroanatomy.
Born in Sainte-Foy-la-Grande, Gironde, France
1844
Graduated from medical school at Hotel Dieu, Paris
1848
Became Prosector of Anatomy at the University of Paris Medical School (the individual who makes dissections for anatomy students), and secretary of the Anatomical Society
1848
Founded a pro-Darwinist society of free thinkers
1849
Performed the first surgery in Europe using hypnotism as anaesthesia
1853
Professor of Surgery at the University of Paris
1856
Published Aneurysms and their Treatment
1859
Founded the Anthropological Society of Paris; published The Ethnology of France
1861
Performed autopsy on M. Leborgne, demonstrated that he has lesions on the frontal cortex of the left hemisphere, locating the area of the brain governing articulate speech
1865
Published General Instructions on Anthropological Research
1867–68
Elected to the chair of External Pathology at the University of Paris Faculty of Medicine, then Professor of Clinical Surgery
1872
Founded The Anthropological Review
1875
Published Instructions on Craniology and Craniometry
1876
Founded the School of Anthropology
9 July 1880
Died in Paris
The human brain has the unique capacity to use language to describe novel situations. The relationships between symbols and their meanings are learned within specific cultural contexts and are not inherited like other biological traits, such as eye colour. Yet the human brain appears to have a predisposition to learn language. This innate ability is supported by specialized brain regions developed in humans. ‘Broca’s area’, in the inferior frontal gyrus, is thought to play a central role in processing syntax, grammar and sentence structure. Patients with damage to this region show symptoms of expressive aphasia (also known as Broca’s aphasia), which is characterized by an inability to produce fluent, grammatical sentences. On the other hand, ‘Wernicke’s area’, situated in the superior temporal gyrus, is involved in the comprehension of language. Damage to this region results in deficits in understanding written and spoken language, a symptom called receptive aphasia (also known as Wernicke’s aphasia). These language areas are directly connected to each other via fibres – called the arcuate fasciculus – and comprise the core of the linguistic brain, predominantly in the left hemisphere.
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The comprehension and production of human language are processed by distinct brain regions within the left hemisphere.
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The first few years in life are critical for learning a first language. Feral children without exposure to language fail to develop full linguistic abilities. They can learn many words, but their syntax never reaches a normal level. Second languages learned during the critical period are processed in the same regions of Broca’s area and Wernicke’s area as the first language, while different regions of Broca’s area are used for a second language learned after puberty.
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3-SECOND BIOGRAPHIES
PAUL BROCA
1824–80
French anatomist and anthropologist (see here)
CARL WERNICKE
1848–1905
German neurologist who found lesions to superior temporal gyrus results in deficits in understanding of language
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Ryota Kanai
Broca’s area is the same in male and female brains. Miscommunication between the sexes takes place in another part of the brain entirely.
How often do you think about thinking? The human brain does not simply convert sensory signals into the execution of actions, but can also assess the quality of its own perceptual experiences, interrogate the reliability of memory, and monitor the results of its own actions. These abilities to access internal mental states through introspection are called ‘metacognition’. We make use of this metacognitive capacity spontaneously in everyday life. One example is when we evaluate our confidence when making a choice. If you are taking an exam, you might be confident in answering some of the questions, but less confident with others. Metacognition is not only important for monitoring how we learn new information, but also for communicating our subjective experiences with others. When you decide what to order in a restaurant, you spontaneously reflect upon your decision by thinking about the experience of eating. In scientific experiments, metacognition is often used as a test of the presence of conscious perception or explicit memory, because we cannot introspect on unconsciously processed information. Current research points to the anterior part of prefrontal cortex – a region particularly expanded in humans through evolution – as key for metacognitive processing.
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Metacognition refers to the awareness of one’s own thought, memory, experience and action as a result of introspective interrogation. It is, literally, cognition about cognition.
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Can animals introspect? What are the differences between the brains of animals that are capable of metacognition and those that aren’t? One way to test for evidence of metacognition in animals is to examine whether they can adjust their behaviour based on the reliability of their decision. Some – such as macaque monkeys, dolphins and rats – exhibit signs of metacognition when performing a perceptual or memory task. Others, such as pigeons, do not.
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3-SECOND BIOGRAPHIES
JOHN FLAVELL
1928–
American developmental psychologist who established metacognition as a research area
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Ryota Kanai
I think therefore I think. This seems to be a particularly human ability. Rodin captured one in flagrante cogito.
From Plato’s charioteer of reason controlling the horse of passion, to Freud’s instinctual id suppressed by the ego, there’s a long tradition of seeing reason and emotion as being in opposition to one another. Translating this perspective to neuroscience, one might imagine that successful decision making depends on the rational frontal lobes controlling the animalistic instincts arising from emotional brain regions that evolved earlier (including the limbic system, found deeper in the brain). But the truth is different: effective decision making is not possible without the motivation and meaning provided by emotional input. Consider Antonio Damasio’s patient, ‘Elliott’. Previously a successful businessman, Elliott underwent neurosurgery for a tumour and lost a part of his brain – the orbitofrontal cortex – that connects the frontal lobes with the emotions. He became a real-life Mr Spock, devoid of emotion. But instead of this making him perfectly rational, he became paralyzed by every decision in life. Damasio later developed the somatic marker hypothesis to describe how visceral emotion supports our decisions. For instance, he showed in a card game that people’s fingers sweat prior to picking up from a losing pile, even before they recognize at a conscious level that they’ve made a bad choice.
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Feelings provide the basis for human reason – brain-damaged patients left devoid of emotion struggle to make the most elementary decisions.
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Although we need emotions to make decisions, their input means we’re not the cold rational agents that traditional economics assumes us to be. For instance, Daniel Kahneman demonstrated with Amos Tversky that the negative emotional impact of losses is twice as intense as the positive effect of gains, which affects our decision making in predictable ways. For one thing, it explains our stubborn reluctance to write off bad investments.
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VOLITION, INTENTION & ‘FREE WILL’
3-SECOND BIOGRAPHIES
DANIEL KAHNEMAN
1934–
Pioneer in the psychology of decision making; published a bestselling popular book about his research in 2011: Thinking Fast and Slow
ANTONIO DAMASIO
1944–
Neurologist, author and researcher, based at the University of Southern California
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Christian Jarrett
Stick or twist? How can I make a rational decision with those two bozos using my frontal lobes as a wrestling dojo?
Mirror neurons were discovered by chance in the 1990s during research conducted in Giacomo Rizzolatti’s laboratory at the University of Parma, Italy. Rizzolatti’s team had been recording the electrical activity of motor neurons in the front of monkeys’ brains, cells known to be involved in the planning and execution of bodily movements. The revelation came when one of the researchers reached for some of the raisins used as treats for the monkeys. To the scientists’ astonishment, they realized that the monkeys’ motor cells had fired, as if they had made the same movement as the researcher. In other words, these cells seemed to have mirror-like properties – they were activated during the execution of an action and by the sight of someone else performing that action. For years the race was on to confirm whether humans have mirror neurons, too – this is no easy task because recording from individual neurons in humans is usually too invasive. However, in 2010, a team led by Roy Mukamel was able to record from hundreds of neurons in the brains of epilepsy patients. The researchers identified a subset of mirror-like cells in the frontal cortex that responded both when the patients performed a given hand gesture or facial expression and when they watched a video of someone else performing those actions.
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Mirror neurons fire when you perform an action or you see someone else perform that same action.
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The discovery of mirror neurons caused huge excitement in the field of neuroscience and beyond, largely because some experts claimed mirror neurons to be the source of human empathy. However, this is disputed. One obvious objection is that we’re quite clearly capable of understanding actions, such as slithering and flying, that we are unable to perform ourselves. The suggestion that autism is caused by a ‘broken’ mirror neuron system also lacks scientific support.
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HOW WE PICK UP A CUP OF COFFEE
3-SECOND BIOGRAPHIES
GIACOMO RIZZOLATTI
1937–
Lead researcher at the University of Parma, where mirror neurons were first discovered
V. S. RAMACHANDRAN
1951–
Influential neuroscientist and author, renowned for his bold claims about mirror neurons (including saying that they will do for psychology what DNA did for biology)
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Christian Jarrett
