Neurologger 3 has been designed to record 16, 32 or 64 neuronal channels having size and weight similar to the second version.
However, neuronal activity usually should be correlated with animal behavior. To record vocalization of the animal, an audio cascade with a microphone capable of recording frequencies up to 100 kHz (200 kHz sampling rate) has been added. Basically, an idea to record ultrasonic vocalizations has been inherited from the previous version of the Neurologger 2B. However, contrary to the previous model, the novel version allows us to record ultrasound simultaneously with 32-channel neuronal activity.
In addition, animal behavior can be tracked by an array of inertial sensors (3-D accelerometer and 3-D gyroscope) complemented by 3-D magnetic compass. All sensors can be polled with the frequencies up to 600 Hz simultaneously with acquiring of neuronal and ultrasonic data.
Similarly to the previous generayion, Neurologger 3 has an infrared receiver for precize synchronization with external equipment with the help of infrared transmitter called Neurologger Synchronizer. This feature has been complemented by Bluetooth tranciver for remote confuguring and data access.
Sampling rates are frely configurable. Two following configurations give an impression about maximal rates:
- 32 neuronal channels 20.833 kHz, sound 125 kHz, motion sensors 579 Hz. Dataflow to memory: 1.77 megabytes per second.
- 32 neuronal channels 15.625 kHz, sound 200 kHz, motion sensors 625 Hz. Dataflow to memory: 1.60 megabytes per second.
Selection of integer sampling rates is also possible. For instance, one can sample 16 channels with frequency 40 kHz, 32 channels with frequency 20 kHz, and 64 channnels with frequency 10 kHz.
The logger consumes about 25 mA from 3.7V Lithium-polymeric battery in these modes.
Weights of the logger parts are shown in the pictures on the right. There are six types of alternative headstages: 16-channel unipolar with Hirose and Omnetics connectors, 32-channel unipolar with Hirose or Omnetics, and 16-channel differential with Hirose or Omnetics that have identical outlook and weight with corresponding 32-channel headstages. The scale is in centimeters. The 64-channel version of Neurologger 3 has two 32-channel headstages attached. One can also use two 16-channel differential headstages to get 32 differential channels in total.
We measured discharge curves of the following Lithium-polymeric 3.7 V batteries (capacity, weight):
20 mAh, 0.63 g
40 mAh, 1.05 g
50 mAh, 1.58 g.
They will provide duration of neuronal recording of 15 min, 1 h 15 min and 2 h 12 min respectively in the above given modes. The discharge curves for the current 25 mA are given on the right.
To simplify attachment of custom-built electrodes we developed wire adapters for both Omnetics and Hirose connectors. One type of wire-adapters for Omnetics and two for Hirose are depicted below.