Brains often unwitting accomplices

On a shopping trip in Melbourne's high-end Chadstone Shopping Centre recently, while enjoying a coffee, entertainer Patti Newton had her handbag snatched.

Stolen items included rings, earrings, bracelets and a set of rosary beads her mother was holding as she died.

Speaking to reporters later that day, a Victoria Police officer recounted that while Newton and daughter Lauren chatted over java and muffins, a man and a woman were paying particularly close attention to them. All of a sudden, the middle-aged woman started a commotion with staff, and while attention was drawn to the fracas, her male companion, similarly aged, stole Newton's bag.

This wrongdoing, apart from being a criminal act and very annoying to Newton, serves to illustrate how the brain - in this case Newton's - processes sounds as well as visual information. And why perhaps Newton's response to the theft was not instantaneous.

Neurons in the brain decipher sound data from the two ears. Doctors use this knowledge to help diagnose the causes of hearing loss based on whether the loss occurs in one ear or both. Given neurons in the brain get sound information from both ears, hearing problems in both ears can indicate damage to parts of the brain that process sound. Conversely, if you have a problem hearing in only one ear, then the cause is likely to be damage to the ear itself, or to the auditory nerve.

The brain can discriminate between different signals received from each ear. This skill is particularly useful in a crowded space, and is referred to as the "cocktail party effect".

In a public space such as a cafe, sounds come from every-which-way, and are of all types - high, low, nasal, baritone and so on. In a crowded room, for instance, the brain solves this sound problem by dedicating one ear to the sound/voice you're struggling to listen to, and the other ear to the balance of the noise in the room.

Your perception of the five senses is a consequence of the interaction of two processes; signals coming from receptors in your body, and activity in brain pathways that responds to these signals - including, in some cases, whether they get passed along to the brain at all. This interaction is apparent in a multitude of phenomena such as petty thieving or pick-pocketing, where, for instance, a two-person operation first distracts the victim's attention, making them look one way, while objects of value (such as a purse) positioned away from her field of view are snatched in the blink of an eyelid.

Sandra Aamodt, the editor of Nature Neuroscience, and Sam Wong, associate professor of Neuroscience and Molecular Biology at Princeton University, in the book Welcome to your Brain introduce readers to the fascinating world of how the brain functions, and in particular, how it manages our relationship with the world.

The human brain - no bigger than a small head of cauliflower - gives us the power to think, plan, speak and imagine. The brain performs a host of functions: it collects a flood of information about the world around us via our five senses; it controls body temperature, blood pressure, heart rate and breathing; it handles physical motion when walking, talking, standing or sitting; and it lets us think, reason, dream and experience emotions.

The authors identify some of the elements that comprise the brain, including neurons, the brain stem, cerebellum, hypothalamus, thalamus, cortex and hippocampus:

• neurons are brain cells that talk to one another and to the rest of the body, whereas glial cells provide essential "behind-the-scenes" support. There are over 100 billion neurons in the brain and even more glial cells;
• the brain stem is where the brain attaches to the spinal cord. It controls the reflexes, heart rate, blood pressure, limb movements and functions such as urination;
• the cerebellum integrates information on the position and movement of limbs;
• the hypothalamus controls behavioural responses including feeding, drinking, sexual response, aggression, hunger, thirst and sleep cycles;
• the thalamus receives sensory information entering the body through the skin, eyes and ears before sending that information to the cortex. The cortex is the largest part of the human brain and interprets (and analyses) sensory information, initiates movement, analyses information, and experiences emotions. It is divided into four parts called lobes: the frontal lobe (responsible for the production of speech and the generation of appropriate behaviour); parietal lobe (receives information from the skin); occipital lobe (responsible for visual perception); and temporal lobe (concerned with hearing and understanding speech);
• the hippocampus is located within the temporal lobe and is vital for short-term memory, including the storage of facts and place information.