Penn Electronic Design Shop uses mass flow control to optimize olfactometer for short-term memory retention research

Advances in science have resulted in a much deeper understanding of the most complex organ in the human body: the brain. One remaining mystery is the mechanism by which a human brain retains and recalls information. The Gottfried lab at the University of Pennsylvania is working hard to solve this mystery through the study of olfaction (the sense of smell).

Their work on olfaction could yield exciting results on the link between short-term memory retention and the brain activity by which it is facilitated.

The experiment

The lab designed an experiment to gain insight into the correlation between scent, short-term memory retention, and brain activity. Here is a brief overview of the experimental process:

  1. Set up an MRI machine to monitor the brain activity of subjects.
  2. Present subjects with a series of three distinct scents.
  3. Wait for a short period of time, varying from 7 to 10 seconds
  4. Introduce subjects to an additional scent.
  5. Subjects then determine if the scent was one of the three above, and in which order they think they initially smelled it.

To facilitate this research, the lab needed a machine to precisely dispense specific volumes of each scent. That’s where Miguel Hernandez, director of the Penn Electronic Design Shop and his team, came in.

Challenge 1: Building an olfactometer to precisely deliver scents

To conduct this experiment, the lab endeavored to develop an olfactometer capable of precisely delivering up to 12 different scents using pneumatics and air pressure. The first iteration of this machine was unable to operate with high enough precision due to valve limitations.

In the Penn Electronic Design Shop, the team improved the electrical design of the olfactometer and streamlined the device. The final version utilizes two Alicat mass flow controllers (MC-20SLPM) to regulate the flow of oxygen through each scent container at established intervals. According to Mr. Hernandez, “there is confidence that the Alicat flow controllers and their measurements will be precise.”

Challenge 2: Interfacing the controllers and solenoid valves at each scent container

The next challenge was interfacing the mass flow controllers and the solenoid valves at each scent container. After discussing the situation with Alicat’s engineering team, Mr. Hernandez tested the analog electronic design and used MatLab software to provide commands to control system. A MatLab open-source software package called PsychToolbox enabled him to create a streamlined command interface, making it easy to adjust the flow controllers and regulate the saturation of oxygen flowing to any given valve.

The real-time parameters displayed on the Alicat controllers’ integrated displays also made it easy for Mr. Hernandez to monitor process outputs and ensure the olfactometer’s electronics were functioning properly.


Olfactometer system


After final testing of the olfactometer, Mr. Hernandez delivered a compact and precise device to the Gottfried lab, tailored exactly to their research parameters. The lab has since used the machine in a variety of research projects, and has found that subjects’ brain activity independently codes for the “what” of the scent and the “when” of the odor sequences.

The team observed that the delay in activity had a direct effect on the later recall of the scent. The results also indicate that certain patterns of brain activity enable multiple memory items that share a common “location” in the brain to be independently maintained, allowing for separate recall.

What is next for the Gottfried lab?

While this project does answer some questions surrounding short-term memory retention and how the brain functions during recall, there is still a lot more work for the Gottfried lab. The team intends to continue using Mr. Hernandez’s olfactometer to learn more about retention and recall of information in the brain.

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