Academic journal article The American Biology Teacher

Picking Your Classmate's Brain: Four Inquiry-Based Experiments about the Human Brain

Academic journal article The American Biology Teacher

Picking Your Classmate's Brain: Four Inquiry-Based Experiments about the Human Brain

Article excerpt


The human brain is a topic of interest to many students yet is seldom explored through laboratory investigation. Here, I describe a means of introducing students to brain research. The four activities outlined below engage students in a true research experience. Students are required to design experiments guided by their hypotheses. Neuropsychological methods are used to study the properties of specific types of brain cells. This approach uses simple equipment and self-reports from human subjects. It is safe, inexpensive, and easy to set up. Optical illusions are used to investigate the property of the cells of the visual system. Depending on the optical illusion selected, students can study retinal photoreceptor cells, thalamic cells of the lateral geniculate nucleus, simple cells, or complex cells of the visual cortex.

* Background

These experiments were devised for a neuroscience undergraduate course taught to a mix of major and nonmajor students. The activity was introduced during a unit on the visual system. The aims were to engage students in the research process, give them familiarity with neuropsychological methods, and have them investigate the properties of cells involved in vision. What follows is a description of the way in which this activity was conducted and an analysis of its successes and challenges. Suggestions for adapting these projects for high school students are provided in a section at the end.

* Vision Research Projects

Below is a brief account of how visual information is conveyed and processed from eye to brain. Readers are referred to any introductory neuroscience textbook (e.g., Pinel, 2006) for a complete explanation of this process. Only information useful for understanding the experiments is offered. Following a description of important cells involved in visual processing, optical illusions whose effects rely on the cells described in the section are introduced, as well as possible ways to modify the basic illusion to investigate the properties of these cells.

* A Summary of Visual Processing

Light that enters the eye stimulates light-sensitive receptors at the back of the eye (Figure 1). The visual data at this point are like a pixelated image. They must be processed by the brain to extract meaning - for example, to identify where objects begin and end and to recognize movement. The visual data collected by the eye are processed in stages by specialized cells in precise areas of the brain. At each step, specific information is obtained, and the processed information is relayed to the next processing center.

* Research Project 1: The Distribution of Rods & Cones in the Retina

Light that enters the eye is detected by receptors called rods and cones. Our ability to perceive colors is conferred by the cones. Cones come in three varieties, each maximally sensitive to a different color: orange, green, or violet (Stein & Stoodley, 2006: p. 119). Rods are more sensitive to light than cones, and they allow us to see in dim light. Since there is only one variety of rods, they do not confer any color information to our nervous system. Light coming from the center of gaze is imaged on the back of the eye in an area called the fovea. The fovea is densely packed with cone receptors. The rest of the eye, which receives light from our peripheral vision, consists mostly of rods. The net consequence of this arrangement is that humans have color vision only in the center of their gaze, and black-and-white vision in the surrounding regions. The precise distributions of rods and cones in the eye have been mapped. The number of cones peaks in the fovea and decreases sharply within 10[degrees] of the center of gaze (Lindsay & Norman, 1977). Rods are absent from the fovea, rise sharply at 20[degrees] from the center of gaze, and slowly decrease in density farther away from the fovea (Lindsay & Norman, 1977). …

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