A system for planning a neurosurgical operation, the system comprising: - an input for receiving functional data and anatomical data of a brain region, and - a processor configured to: analyze the functional data to identify functional connections in the brain region wherein the functional connections are based on repeated, simultaneous or correlated neural activity in different regions of the brain region, and to form a network representation of the functional connections, the network representation comprising network nodes and network connections interconnecting the network nodes, map the network representation of the functional connections and the anatomical data to a common coordinate system, perform a topological network analysis of the network representation, the processor being further configured to calculate clustering coefficients of the network nodes for performing the topological network analysis of the network representation, identify critical network nodes, wherein the critical network nodes are identified as network nodes having a high clustering coefficient representing a high connectivity density, on the basis of said topological network analysis, perform a simulated removal of one of the network nodes from the network representation and determine an expected function loss associated with the simulated removal on the basis of changes in the network representation resulting from said removal, and - an output for providing a visual representation of the network representation as an overlay over the anatomical data, wherein the critical network nodes are highlighted in the visual presentation. - an input for receiving functional data and anatomical data of a brain region, and - a processor configured to: analyze the functional data to identify functional connections in the brain region wherein the functional connections are based on repeated, simultaneous or correlated neural activity in different regions of the brain region, and to form a network representation of the functional connections, the network representation comprising network nodes and network connections interconnecting the network nodes, map the network representation of the functional connections and the anatomical data to a common coordinate system, perform a topological network analysis of the network representation, the processor being further configured to calculate clustering coefficients of the network nodes for performing the topological network analysis of the network representation, identify critical network nodes, wherein the critical network nodes are identified as network nodes having a high clustering coefficient representing a high connectivity density, on the basis of said topological network analysis, perform a simulated removal of one of the network nodes from the network representation and determine an expected function loss associated with the simulated removal on the basis of changes in the network representation resulting from said removal, and analyze the functional data to identify functional connections in the brain region wherein the functional connections are based on repeated, simultaneous or correlated neural activity in different regions of the brain region, and to form a network representation of the functional connections, the network representation comprising network nodes and network connections interconnecting the network nodes, map the network representation of the functional connections and the anatomical data to a common coordinate system, perform a topological network analysis of the network representation, the processor being further configured to calculate clustering coefficients of the network nodes for performing the topological network analysis of the network representation, identify critical network nodes, wherein the critical network nodes are identified as network nodes having a high clustering coefficient representing a high connectivity density, on the basis of said topological network analysis, perform a simulated removal of one of the network nodes from the network representation and determine an expected function loss associated with the simulated removal on the basis of changes in the network representation resulting from said removal, and - an output for providing a visual representation of the network representation as an overlay over the anatomical data, wherein the critical network nodes are highlighted in the visual presentation.