1. The document discusses measuring the electrical conductivity of brain tissue using different methods, finding values ranging from 0.01 to 0.7 S/m. 2. A 1D method using a syringe produced the most encouraging results so far. 3. Further studies aim to measure conductivity changes before, during, and after seizure-like events in mouse cortex to explore links between seizures and conductivity.

1. Measuring Electrical Conductivity of Brain Tissue By: Maher Elbohouty Supervisors: Dr Marcus Wilson AProf Alistair Steyn-Ross 15 November 2011

3. … slicing… Brain removal… 15 November 2011 © THE UNIVERSITY OF WAIKATO

5. 1. Modified syringe and two stainless steel plate electrodes ( Flat Electrodes): 15 November 2011 © THE UNIVERSITY OF WAIKATO

6. Taking the sample .. 15 November 2011 © THE UNIVERSITY OF WAIKATO

7. The resistivity of brain slices at 10 kHz 15 November 2011 © THE UNIVERSITY OF WAIKATO The Syringe (V3) digital calliper (DIGMATIC- Mitutoyo Corporation, Model CD-6”) and LCR meter (Agilent E4980A)

8. Defining equation in 1D 15 November 2011 © THE UNIVERSITY OF WAIKATO RA/  a (m) x (m) Slice ACSF  s  a

9. Measurement of resistance (R) against different separation of electrodes (x) 15 November 2011 © THE UNIVERSITY OF WAIKATO

13. 2. 2D Electrical conductivity by 4 Cylindrical electrodes 15 November 2011 © THE UNIVERSITY OF WAIKATO

15. Defining equation in 2D 15 November 2011 © THE UNIVERSITY OF WAIKATO For the ACSF we expect the relationship: Where:  : is the fluid conductivity I : the measured current. D : the depth of the fluid  : the voltage  r 1 : distance between I in and V 2 . r 2 : distance between I out and V 2 . r 3 : distance between I in and V 1 . r 4 : distance between I out and V 1 .

20. What is the problem? mouse brain slices 15 November 2011 © THE UNIVERSITY OF WAIKATO 1 cm

25. Modelling : The approximate calculation our equation is supported by more accurate computer modelling of the electric fields between the three-dimensional electrodes using COMSOL Multiphysics. We have used COMSOL Multiphysics to investigate electric field between the array. 15 November 2011 © THE UNIVERSITY OF WAIKATO Modeling shows very high current density on the electrodes which make them burning