Alcohol affects the entire brain because it reaches all areas of the brain. However, different parts of the brain are responsible for different functions, such as motor control, thinking, alertness, sensations, speech, coordination, and balance. Below is a list of several of the intoxicating effects of alcohol and the corresponding brain regions affected by alcohol:
- Excitation (disinhibition): a normally functioning frontal cortex helps to suppress or inhibit behaviors that are socially inappropriate and impulsive. Alcohol releases this “brake” within the frontal cortex.
- Pleasure: the “pleasure or reward pathway” extends from the midbrain area to the limbic system (involved in emotion). Although not actually a symptom of intoxication, it is the pleasurable feeling that reinforces someone to keep drinking.
- Loss of judgment: the frontal cortex also controls judgment, thinking, decision-making, and risk-taking behavior.
- Slowed reaction time: the motor cortex (frontal lobe) and the sensory cortex (parietal lobe) or visual cortex (occipital lobe) work together to coordinate sensory information coming in to the brain (such as touch or vision) with the reaction instructions going out of the brain to perform some type of movement.
Figure 2.2 Symptoms of alcohol intoxication are produced in different brain regions. One of the first areas affected as intoxication develops is the frontal cortex–leading to loss of judgement.
- Unsteady gait: the cerebellum, located underneath in the back of the brain, controls balance and coordination.
- Nausea and vomiting: In the brainstem, or medulla, there is a tiny area that controls vomiting “the vomiting center”. Right next door, there is an area called the “chemoreceptor trigger zone”. Receptors in this zone sense when there is a toxic substance in the blood and send neural signals to the stomach to vomit as a protective action. Click here to read about potential fatal effects of vomiting while intoxicated.
- Sedation: several areas of the brain participate in maintaining alertness; these range from the brainstem up to the cerebral cortex.
- Loss of memory: the hippocampus lies deep inside the brain; it controls learning and memory. An inability to recall events during and after drinking is called a blackout. It occurs because alcohol prevents the hippocampus from consolidating the information that actually forms the memory.
- Loss of consciousness: complete depression of activity in the cerebral cortex leads to a loss of all thought, speech, and motor control. However, vital functions (breathing, heart rate) are still preserved.
- Respiratory depression: the brainstem, at the bottom of the brain, is an area that governs many vital functions such as breathing, heart rate, and blood pressure. It is a good thing that the neurons in the brainstem are least sensitive to alcohol.